Hacker's Handbook
Ok just a quick note, this is a very early version of the book and
was later banned. We've done our best in converting it to ASCII.
It's taken us some time to put it together because of the
reformatting, so I hope it's appreciated. We have kept to the
original page numbering for so that the index will be correct.

Compliments Electronic Images - Gizmo

                        Century Communications

                               - T H E -

                          - H A C K E R ' S -

                          - H A N D B O O K -

                      Copyright (c) Hugo Cornwall

                          All rights reserved

First published in Great Britain in 1985 by Century Communications Ltd
Portland House, 12-13 Greek Street, London W1V 5LE.

Reprinted 1985 (four times)

ISBN 0 7126 0650 5

Printed and bound in Great Britain by Billing & Sons Limited, Worcester.


Introduction                                                     vii

First Principles

2 Computer-to-computer communications                             7

3 Hackers' Equipment                                             15

4 Targets: What you can find on mainframes                       30

5 Hackers' Intelligence                                          42

6 Hackers' Techniques                                            57

7 Networks                                                       69

8 Viewdata systems                                               86

9 Radio computer data                                            99

10 Hacking: the future                                          108


I troubleshooting                                               112
II Glossary                                                     117
III CCITT and related standards                                 130
IV Standard computer alphabets                                  132
V Modems                                                        141
VI Radio Spectrum                                               144
VII Port-finder flow chart                                      148


   The word 'hacker' is used in two different but associated
ways: for some, a hacker is merely a computer enthusiast of any kind,
who loves working with the beasties for their own sake, as opposed to
operating them in order to enrich a company or research project --or
to play games.

   This book uses the word in a more restricted sense: hacking is a
recreational and educational sport. It consists of attempting to make
unauthorised entry into computers and to explore what is there. The
sport's aims and purposes have been widely misunderstood; most
hackers are not interested in perpetrating massive frauds, modifying
their personal banking, taxation and employee records, or inducing
one world super-power into inadvertently commencing Armageddon in the
mistaken belief that another super-power is about to attack it. Every
hacker I have ever come across has been quite clear about where the
fun lies: it is in developing an understanding of a system and
finally producing the skills and tools to defeat it. In the vast
majority of cases, the process of 'getting in' is much more
satisfying than what is discovered in the protected computer files.

   In this respect, the hacker is the direct descendant of the phone
phreaks of fifteen years ago. Phone phreaking became interesting as
intra-nation and international subscriber trunk dialling was
introduced, but when the London-based phreak finally chained his way
through to Hawaii, he usually had no one there to speak to except the
local weather service or American Express office, to confirm that the
desired target had indeed been hit. One of the earliest of the
present generation of hackers, Susan Headley, only 17 when she began
her exploits in California in 1977, chose as her target the local
phone company and, with the information extracted from her hacks, ran
all over the telephone network. She 'retired' four years later, when
friends started developing schemes to shut down part of the phone

   There is also a strong affinity with program copy-protection
crunchers. Most commercial software for micros is sold in a form to
prevent obvious casual copying, say by loading a cassette, cartridge
or disk into memory and then executing a 'save' on to a

** Page VII

blank cassette or disk.  Copy-protection devices vary greatly in
their methodology and sophistication and there are those who, without
any commercial motive, enjoy nothing so much as defeating them. Every
computer buff has met at least one cruncher with a vast store of
commercial programs, all of which have somehow had the protection
removed--and perhaps the main title subtly altered to show the
cruncher's technical skills--but which are then never actually used
at all.

   Perhaps I should tell you what you can reasonably expect from this
handbook.  Hacking is an activity like few others: it is semi-legal,
seldom encouraged, and in its full extent so vast that no individual
or group, short of an organisation like GCHQ or NSA, could hope to
grasp a fraction of the possibilities. So this is not one of those
books with titles like Games Programming with the 6502 where, if the
book is any good and if you are any good, you will emerge with some
mastery of the subject-matter. The aim of this book is merely to give
you some grasp of methodology, help you develop the appropriate
attitudes and skills, provide essential background and some
referencing material--and point you in the right directions for more
knowledge. Up to a point, each chapter may be read by itself; I have
compiled extensive appendices, containing material which will be of
use long after the main body of the text has been absorbed.

   It is one of the characteristics of hacking anecdotes, like those
relating to espionage exploits, that almost no one closely involved
has much stake in the truth; victims want to describe damage as
minimal, and perpetrators like to paint themselves as heroes while
carefully disguising sources and methods. In addition, journalists
who cover such stories are not always sufficiently competent to write
accurately, or even to know when they are being hoodwink- ed. (A note
for journalists: any hacker who offers to break into a system on
demand is conning you--the most you can expect is a repeat
performance for your benefit of what a hacker has previously
succeeded in doing. Getting to the 'front page' of a service or
network need not imply that everything within that service can be
accessed. Being able to retrieve confidential information, perhaps
credit ratings, does not mean that the hacker would also be able to
alter that data. Remember the first rule of good reporting: be
sceptical.) So far as possible, I have tried to verify each story
that appears in these pages, but hackers work in isolated groups and
my sources on some of the important hacks of recent years are more
remote than I would have liked. In these

** Page VIII

cases, my accounts are of events and methods which, in all the
circumstances, I believe are true. I welcome notes of correction.

   Experienced hackers may identify one or two curious gaps in the
range of coverage, or less than full explanations; you can chose any
combination of the following explanations without causing me any
worry: first, I may be ignorant and incompetent; second, much of the
fun of hacking is making your own discoveries and I wouldn't want to
spoil that; third, maybe there are a few areas which are really best
left alone.

   Nearly all of the material is applicable to readers in all
countries; however, the author is British and so are most of his

   The pleasures of hacking are possible at almost any level of
computer competence beyond rank beginner and with quite minimal
equipment. It is quite difficult to describe the joy of using the
world's cheapest micro, some clever firmware, a home-brew acoustic
coupler and find that, courtesy of a friendly remote PDP11/70, you
can be playing with Unix, the fashionable multitasking operating

   The assumptions I have made about you as a reader are that you own a
modest personal computer, a modem and some communications software
which you know, roughly, how to use. (If you are not confident yet,
practise logging on to a few hobbyist bulletin boards.) For more
advanced hacking, better equipment helps; but, just as very tasty
photographs can be taken with snap-shot cameras, the computer
equivalent of a Hasselblad with a trolley- load of accessories is not

   Since you may at this point be suspicious that I have vast
technical resources at my disposal, let me describe the kit that has
been used for most of my network adventures. At the centre is a
battered old Apple II+, its lid off most of the time to draw away the
heat from the many boards cramming the expansion slots. I use an
industry standard dot matrix printer, famous equally for the variety
of type founts possible, and for the paper-handling path, which
regularly skews off. I have two large boxes crammed full of software,
as I collect comms software in particular like a deranged
philatelist, but I use one package almost exclusively. As for
modems--well, at this point the set-up does become unconventional; by
the phone point are jack sockets for BT 95A, BT 96A, BT 600 and a
North American modular jack. I have two acoustic couplers, devices
for plunging telephone handsets into so that the computer can talk
down the line, at operating speeds of 300/300 and 75/1200. I also
have three heavy, mushroom coloured 'shoe-boxes', representing modem
technology of 4 or 5 years ago and operating at various speeds and
combinations of duplex/half- duplex. Whereas the acoustic coupler
connects my computer to the line by audio, the modem links up at the
electrical level and is more accurate and free from error. I have
access to other equipment in my work and through friends, but this is
what I use most of the time.

** Page IX

Behind me is my other important bit of kit: a filing cabinet.
Hacking is not an activity confined to sitting at keyboards and
watching screens. All good hackers retain formidable collections of
articles, promotional material and documentation; read on, and you
will see why.
   Finally, to those who would argue that a hacker's handbook must be
giving guidance to potential criminals, I have two things to say:
First, few people object to the sports of clay-pigeon shooting or
archery, although rifles, pistols and crossbows have no 'real'
purpose other than to kill things--and hackers have their own code of
responsibility, too. Second, real hacking is not as it is shown in
the movies and on tv, a situation which the publication of this book
may do something to correct.  The sport of hacking itself may involve
breach of aspects of the law, notably theft of electricity, theft of
computer time and unlicensed usage of copyright material; every
hacker must decide individually each instance as it arises.
   Various people helped me on various aspects of this book; they
must all remain unnamed--they know who they are and that they have my

** Page X


First Principles
   The first hack I ever did was executed at an exhibition stand run
by BT's then rather new Prestel service. Earlier, in an adjacent
conference hall, an enthusiastic speaker had demonstrated view-
data's potential world-wide spread by logging on to Viditel, the
infant Dutch service. He had had, as so often happens in the these
circumstances, difficulty in logging on first time. He was using one
of those sets that displays auto-dialled telephone numbers; that was
how I found the number to call. By the time he had finished his third
unsuccessful log-on attempt I (and presumably several others) had all
the pass numbers. While the BT staff were busy with other visitors to
their stand, I picked out for myself a relatively neglected viewdata
set. I knew that it was possible to by-pass the auto-dialler with its
pre-programmed phone numbers in this particular model, simply by
picking up the the phone adjacent to it, dialling my preferred
number, waiting for the whistle, and then hitting the keyboard button
labelled 'viewdata'. I dialled Holland, performed my little by-pass
trick and watched Viditel write itself on the screen. The pass
numbers were accepted first time and, courtesy of...no, I'll spare
them embarrassment...I had only lack of fluency in Dutch to restrain
my explorations.  Fortunately, the first BT executive to spot what I
had done was amused as well.

   Most hackers seem to have started in a similar way. Essentially
you rely on the foolishness and inadequate sense of security of
computer salesmen, operators, programmers and designers.

   In the introduction to this book I described hacking as a sport;
and like most sports, it is both relatively pointless and filled with
rules, written or otherwise, which have to be obeyed if there is to
be any meaningfulness to it. Just as rugby football is not only about
forcing a ball down one end of a field, so hacking is not just about
using any means to secure access to a computer.

   On this basis, opening private correspondence to secure a password
on a public access service like Prestel and then running around the
system building up someone's bill, is not what hackers call hacking.
The critical element must be the use of skill in some shape or form.

** Page 1

   Hacking is not a new pursuit. It started in the early 1960s when
the first "serious" time-share computers began to appear at
university sites. Very early on, 'unofficial' areas of the memory
started to appear, first as mere notice boards and scratch pads for
private programming experiments, then, as locations for games.
(Where, and how do you think the early Space Invaders, Lunar Landers
and Adventure Games were created?) Perhaps tech-hacking-- the
mischievous manipulation of technology--goes back even further. One
of the old favourites of US campus life was to rewire the control
panels of elevators (lifts) in high-rise buildings, so that a request
for the third floor resulted in the occupants being whizzed to the

   Towards the end of the 60s, when the first experimental networks
arrived on the scene (particularly when the legendary
ARPAnet--Advanced Research Projects Agency network-- opened up), the
computer hackers skipped out of their own local computers, along the
packet-switched high grade communications lines, and into the other
machines on the net. But all these hackers were privileged
individuals. They were at a university or research resource, and they
were able to borrow terminals to work with.

   What has changed now, of course, is the wide availability of home
computers and the modems to go with them, the growth of public-access
networking of computers, and the enormous quantity and variety of
computers that can be accessed.

   Hackers vary considerably in their native computer skills; a basic
knowledge of how data is held on computers and can be transferred
from one to another is essential. Determination, alertness,
opportunism, the ability to analyse and synthesise, the collection of
relevant helpful data and luck--the pre-requisites of any
intelligence officer--are all equally important. If you can write
quick effective programs in either a high level language or machine
code, well, it helps. A knowledge of on-line query procedures is
helpful, and the ability to work in one or more popular mainframe and
mini operating systems could put you in the big league.

   The materials and information you need to hack are all around
you--only they are seldom marked as such.  Remember that a large
proportion of what is passed off as 'secret intelligence' is openly
available, if only you know where to look and how to appreciate what
you find. At one time or another, hacking will test everything you
know about computers and communications. You will discover your
abilities increase in fits and starts, and you must

** Page 2

be prepared for long periods when nothing new appears to happen.

   Popular films and tv series have built up a mythology of what
hackers can do and with what degree of ease. My personal delight in
such Dream Factory output is in compiling a list of all the mistakes
in each episode. Anyone who has ever tried to move a graphics game
from one micro to an almost-similar competitor will already know that
the chances of getting a home micro to display the North Atlantic
Strategic Situation as it would be viewed from the President's
Command Post would be slim even if appropriate telephone numbers and
passwords were available. Less immediately obvious is the fact that
most home micros talk to the outside world through limited but
convenient asynchronous protocols, effectively denying direct access
to the mainframe products of the world's undisputed leading computer
manufacturer, which favours synchronous protocols. And home micro
displays are memory-mapped, not vector-traced...  Nevertheless, it is
astonishingly easy to get remarkable results. And thanks to the
protocol transformation facilities of PADs in PSS networks (of which
much more later), you can get into large IBM devices....

   The cheapest hacking kit I have ever used consisted of a ZX81, 16K
RAMpack, a clever firmware accessory and an acoustic coupler. Total
cost, just over 100. The ZX81's touch-membrane keyboard was one
liability; another was the uncertainty of the various connectors.
Much of the cleverness of the firmware was devoted to overcoming the
native drawbacks of the ZX81's inner configuration--the fact that it
didn't readily send and receive characters in the industry-standard
ASCII code, and that the output port was designed more for instant
access to the Z80's main logic rather than to use industry-standard
serial port protocols and to rectify the limited screen display.

   Yet this kit was capable of adjusting to most bulletin boards;
could get into most dial-up 300/300 asynchronous ports,
re-configuring for word-length and parity if needed; could have
accessed a PSS PAD and hence got into a huge range of computers not
normally available to micro-owners; and, with another modem, could
have got into viewdata services. You could print out pages on the ZX
'tin-foil' printer. The disadvantages of this kit were all in
convenience, not in facilities. Chapter 3 describes the sort of kit
most hackers use.

   It is even possible to hack with no equipment at all. All major
banks now have a network of 'hole in the wall' cash machines-- ATMs
or Automatic Telling Machines, as they are officially

** Page 3

known. Major building societies have their own network. These
machines have had faults in software design, and the hackers who
played around with them used no more equipment than their fingers and
brains. More about this later.

   Though I have no intention of writing at length about hacking
etiquette, it is worth one paragraph: lovers of fresh-air walks obey
the Country Code; they close gates behind them, and avoid damage to
crops and livestock. Something very similar ought to guide your
rambles into other people's computers: don't manipulate files unless
you are sure a back-up exists; don't crash operating systems; don't
lock legitimate users out from access; watch who you give information
to; if you really discover something confidential, keep it to
yourself.  Hackers should not be interested in fraud.  Finally, just
as any rambler who ventured past barbed wire and notices warning
about the Official Secrets Acts would deserve whatever happened
thereafter, there are a few hacking projects which should never be

   On the converse side, I and many hackers I know are convinced of one
thing: we receive more than a little help from the system managers of
the computers we attack. In the case of computers owned by
universities and polys, there is little doubt that a number of them
are viewed like academic libraries--strictly speaking they are for
the student population, but if an outsider seriously thirsty for
knowledge shows up, they aren't turned away. As for other computers,
a number of us are almost sure we have been used as a cheap means to
test a system's defences...someone releases a phone number and
low-level password to hackers (there are plenty of ways) and watches
what happens over the next few weeks while the computer files
themselves are empty of sensitive data. Then, when the results have
been noted, the phone numbers and passwords are changed, the security
improved etc etc....much easier on dp budgets than employing
programmers at 150/man/ day or more. Certainly the Pentagon has been
known to form 'Tiger Units' of US Army computer specialists to
pin-point weaknesses in systems security.

   Two spectacular hacks of recent years have captured the public
imagination: the first, the Great Prince Philip Prestel Hack, is
described in detail in chapter 8, which deals with viewdata. The
second was spectacular because it was carried out on live national
television. It occurred on October 2nd 1983 during a follow-up to the
BBC's successful Computer Literacy series. It's worth reporting here,
because it neatly illustrates the essence of hacking as a sport...
skill with systems, careful research, maximum impact

** Page 4

with minimum real harm, and humour.

   The tv presenter, John Coll, was trying to show off the Telecom
Gold electronic mail service. Coll had hitherto never liked long
passwords and, in the context of the tight timing and pressures of
live tv, a two letter password seemed a good idea at the time. On
Telecom Gold, it is only the password that is truly confidential;
system and account numbers, as well as phone numbers to log on to the
system, are easily obtainable. The BBC's account number, extensively
publicised, was OWL001, the owl being the 'logo' for the tv series as
well as the BBC computer.

   The hacker, who appeared on a subsequent programme as a 'former
hacker' and who talked about his activities in general, but did not
openly acknowledge his responsibility for the BBC act, managed to
seize control of Coll's mailbox and superimpose a message of his own:

Computer Security Error. Illegal access. I hope your television
PROGRAMME runs as smoothly as my PROGRAM worked out your passwords!
Nothing is secure!

                         Hackers' Song
            "Put another password in,
            Bomb it out and try again
            Try to get past logging in,
            We're hacking, hacking, hacking

            Try his first wife's maiden name,
            This is more than just a game,
            It's real fun, but just the same,
            It's hacking, hacking, hacking"

                                        The Nutcracker (Hackers UK)


   After the hack a number of stories about how it had been carried
out, and by whom, circulated; it was suggested that the hackers had
crashed through to the operating system of the Prime computers upon
which the Dialcom electronic mail software

** Page 5

resided--it was also suggested that the BBC had arranged the whole
thing as a stunt, or alternatively, that some BBC employees had fixed
it up without telling their colleagues. Getting to the truth of a
legend in such cases is almost always impossible. No one involved has
a stake in the truth. British Telecom, with a strong commitment to
get Gold accepted in the business community, was anxious to suggest
that only the dirtiest of dirty tricks could remove the inherent
confidentiality of their electronic mail service. Naturally, the
British Broadcasting Corporation rejected any possibility that it
would connive in an irresponsible cheap stunt. But the hacker had no
great stake in the truth either--he had sources and contacts to
protect, and his image in the hacker community to bolster. Never
expect any hacking anecdote to be completely truthful.

** Page 6



   Services intended for access by microcomputers are nowadays
usually presented in a very user-friendly fashion: pop in your
software disc or firmware, check the connections, dial the telephone
number, listen for the tone...and there you are.  Hackers, interested
in venturing where they are not invited, enjoy no such luxury. They
may want to access older services which preceded the modern 'human
interface'; they are very likely to travel along paths intended, not
for ordinary customers, but for engineers or salesmen; they could be
utilising facilities that were part of a computer's commissioning
process and have been hardly used since.

So the hacker needs a greater knowledge of datacomms technology than
does a more passive computer user, and some feeling for the history
of the technology is pretty essential, because of its growth pattern
and because of the fact that many interesting installations still use
yesterday's solutions.

   Getting one computer to talk to another some distance away means
accepting a number of limiting factors:

 * Although computers can send out several bits of information at
once, the ribbon cable necessary to do this is not economical at any
great length, particularly if the information is to be sent out over
a network--each wire in the ribbon would need switching separately,
thus making ex- changes prohibitively expensive. So bits must be
transmitted one at a time, or serially.

** Page 7

 * Since you will be using, in the first instance, wires and networks
already installed--in the form of the telephone and telex
networks--you must accept that the limited bandwidth of these
facilities will restrict the rate at which data can be sent. The data
will pass through long lengths of wire, frequently being
re-amplified, and undergoing de- gradation as it passes through dirty
switches and relays in a multiplicity of exchanges.

 * Data must be easily capable of accurate recovery at the far end.

 * Sending and receiving computers must be synchronised in their

 * The mode in which data is transmitted must be one understood by
all computers; accepting a standard protocol may mean adopting the
speed and efficiency of the slowest.

 * The present 'universal' standard for data transmission used by
microcomputers and many other services uses agreed tones to signify
binary 0 and binary 1, the ASCII character set (also known as
International Alphabet No 5), and an asynchronous protocol, whereby
the transmitting and receiving computers are locked in step every
time a character is sent, not just at the beginning of a transmission
stream. Like nearly all standards, it is highly arbitrary in its
decisions and derives its importance simply from the fact of being
generally accepted. Like many standards, too, there are a number of
subtle and important variations.

   To see how the standard works, how it came about and the reasons
for the variations, we need to look back a little into history.

The Growth of Telegraphy

   The essential techniques of sending data along wires has a history
of 150 years, and some of the common terminology of modern data
transmission goes right back to the first experiments.

   The earliest form of telegraphy, itself the earliest form of
electrical message sending, used the remote actuation of electrical
relays to leave marks on a strip of paper. The letters of the
alphabet were defined by the patterns of 'mark' and 'space'.

** Page 8

   The terms have come through to the present, to signify binary
conditions of '1' and '0' respectively. The first reliable machine
for sending letters and figures by this method dates from 1840; the
direct successor of that machine, using remarkably unchanged
electromechanical technology and a 5-bit alphabetic code, is still
widely used today, as the telex/teleprinter/teletype. The mark and
space have been replaced by holes punched in paper-tape: larger holes
for mark, smaller ones for space. Synchronisation between sending and
receiving stations is carried out by beginning each letter with a
'start' bit (a space) and concluding it with a 'stop' bit (mark). The
'idle' state of a circuit is thus 'mark'. In effect, therefore, each
letter requires the transmission of 7 bits:

. * * . . . * (letter A: . = space; * = mark)

of which the first . is the start bit, the last * is the stop bit and
* * . .. is the code for A.

   This is the principle means for sending text messages around the
world, and the way in which news reports are distributed globally.
And, until third-world countries are rich enough to afford more
advanced devices, the technology will survive.

Early computer communications

  When, 110 years after the first such machines came on line, the
need arose to address computers remotely, telegraphy was the obvious
way to do so. No one expected computers in the early 1950s to give
instant results; jobs were assembled in batches, often fed in by
means of paper-tape (another borrowing from telex, still in use) and
then run. The instant calculation and collation of data was then
considered quite miraculous. So the first use of data communications
was almost exclusively to ensure that the machine was fed with
up-to-date information, not for the machine to send the results out
to those who might want it; they could wait for the 'print-out' in
due course, borne to them with considerable solemnity by the computer
experts. Typical communications speeds were 50 or 75 baud. (The baud
is the measure of speed of data transmission: specifically, it refers
to the number of signal level changes per second and is thus not the
same as bits-per-second.)

   These early computers were, of course, in today's jargon,
single-user/single-task; programs were fed by direct machine coding.
Gradually, over the next 15 years, computers spawned multi-user
capabilities by means of time-sharing techniques, and their human
interface became more 'user-friendly'.

** Page 9

With these facilities grew the demand for remote access to
computers, and modern data communications began.

   Even at the very end of the 1960s when I had my own very first
encounter with a computer, the links with telegraphy were still
obvious. As a result of happenstance, I was in a Government-run
research facility to the south-west of London, and the program I was
to use was located on a computer just to the north of Central London;
I was sat down in front of a battered teletype--capitals and figures
only, and requiring not inconsiderable physical force from my
smallish fingers to actuate the keys of my choice. As it was a
teletype outputting on to a paper roll, mistakes could not as readily
be erased as on a VDU, and since the sole form of error reporting
consisted of a solitary ?, the episode was more frustrating than
thrilling. VDUs and good keyboards were then far too expensive for
'ordinary' use.

The telephone network

   But by that time all sorts of changes in datacomms were taking
place. The telex and telegraphy network, originally so important, had
long been overtaken by voice-grade telephone circuits (Bell's
invention dates from 1876). For computer communication, mark and
space could be indicated by different audio tones, rather than by
different voltage conditions. Data traffic on a telex line can
operate in only one direction at a time, but, by selecting different
pairs of tones, both 'transmitter' and 'receiver' could speak
simultaneously--so that in fact, one has to talk about 'originate'
and 'answer' instead.

   Improved electrical circuit design meant that higher speeds than
50 or 75 baud became possible; there was a move to 110 baud, then 300
and, so far as ordinary telephone circuits are concerned, 1200 baud
is now regarded as the top limit.

   The 'start' and 'stop' method of synchronising the near and far
end of a communications circuit at the beginning of each individual
letter has been retained, but the common use of the 5-bit Baudot code
has been replaced by a 7-bit extended code which allows for many more
characters, 128 in fact.

   Lastly, to reduce errors in transmission due to noise in the
telephone line and circuitry, each letter can be checked by the use
of a further bit (the parity bit), which adds up all the bits in the
main character and then, depending on whether the result is odd or
even, adds a binary 0 or binary 1.

   The full modern transmission of a letter in this system, in this
case, K, therefore, looks like this:

** Page 10


                     1       1           1       1   1       1
             Mark  +---+   +---+       +---+   +---+---+   +---+
LINE               |   | 0 |   | 0   0 |   | 0 |       | 0 |   |
CONDITION    Space-+   +---+   +---+---+   +---+       +---+   +-

                   ^   ^
                   |   |
BINARY        STOP-+  START  1   0   0   1   0   1   1   0

   The first 0 is the start bit; then follows 7 bits of the actual
letter code (1001011); then the parity bit; then the final 1 is the
stop code.

   This system, asynchronous start-stop ASCII (the common name for
the alphabetic code), is the basis for nearly all micro-based
communications. The key variations relate to:

bit-length; you can have 7 or 8 databits (*)

parity; (it can be even or odd, or entirely absent),

Tones - The tones used to signify binary 0 and binary 1, and which
computer is in 'originate' and which in 'answer', can vary according
to the speed of the transmission and also to whether the service is
used in North America or the rest of the world.  (Briefly, most of
the world uses tones and standards laid down by the Geneva-based
organisation, CCITT, a specialised agency of the International
Telecommunications Union; whereas in the United States and most parts
of Canada, tones determined by the telephone utility, colloquially
known as Ma Bell, are adopted.) The following table gives the
standards and tones in common use.

(*) There are no 'obvious explanations' for the variations commonly
found: most electronic mail services and viewdata transmit 7 data
bits, even parity and I stop Bit; Telecom Gold and most hobbyist
bulletin boards transmit 8 data bits, odd parity and 1 stop bit.
Terminal emulator software--see chapter 3--allows users to adjust for
these differing requirements.

** Page 11

Service        Speed  Duplex  Transmit    Receive     Answer
Designator                    0    1      0     1

V21 orig       300(*) full    1180  980   1850  1650   -
V21 ans        300(*) full    1850 1650   1180   980  2100
V23 (1)        600    half    1700 1300   1700  1300  2100
V23 (2)       1200    f/h(**) 2100 1300   2100  1300  2100
V23 back        75    f/h(**)  450  390    450   390   -
Bell 103 orig  300(*) full    1070 1270   2025  2225   -
Bell 103 ans   300(*) full    2025 2225   1070  1270  2225
Bell 202      1200    half    2200 1200   2200  1200  2025

(*)any speed up to 300 baud, can also include 75 and 110 baud

(**)service can either be half-duplex at 1200 baud or asymmetrical
full duplex, with 75 baud originate and 1200 baud receive (commonly
used as viewdata user) or 1200 transmit and 75 receive (viewdata

Higher Speeds

   1200 baud is usually regarded as the fastest speed possible on an
ordinary voice-grade telephone line. Beyond this, noise on the line
due to the switching circuits at the various telephone exchanges,
poor cabling, etc.  make accurate transmission difficult. Indeed, at
higher speeds it becomes increasingly important to use transmission
protocols that include error correction.

   Error correction techniques usually consist of dividing the
transmission stream into a series of blocks which can be checked, one
at a time, by the receiving computer. The 'parity' system mentioned
above is one example, but obviously a crude one. The difficulty is
that the more secure an error-correction protocol becomes, the
greater becomes the overhead in terms of numbers of bits transmitted
to send just one character from one computer to another. Thus, in the
typical 300 bit situation, the actual letter is defined by 7 bits,
'start' and 'stop' account for another two, and the check takes a
further one--ten in all. After a while, what you gain in the speed
with which each actual bit is transmitted, you lose, because so many
bits have to be sent to ensure that a single character is accurately

** Page 12

   Although some people risk using 2400 baud on ordinary telephone
lines--the jargon is the PTSN (Public Telephone Switched
Network)--this means using expensive modems. Where higher speeds are
essential, leased circuits, not available via dial-up. become
essential. The leased circuit is paid for on a fixed charge, not a
charge based on time-connected. Such circuits can be conditioned',
for example by using special amplifiers, to support the higher data

   For really high speed transmissions, however, pairs of copper
cable are inadequate. Medium speed is obtainable by the use of
coaxial cable (a little like that used for tv antenna hook-ups) which
have a very broad bandwidth. Imposing several different channels on
one cable-length is called multiplexing and, depending on the
application, the various channels can either carry several different
computer conversations simultaneously or can send several bits of one
computer conversation in parallel, just as though there were a ribbon
cable between the two participating computers. Either way, what
happens is that each binary 0 or binary 1 is given, not an audio
tone, but a radio frequency tone.

Synchronous Protocols

   In the asynchronous protocols so far described, transmitting and
receiving computers are kept in step with each other every time a
character is sent, via the 'start' and 'stop' bits. In synchronous
comms, the locking together is done merely at the start of each block
of transmission by the sending of a special code (often SYN). The SYN
code starts a clock (a timed train of pulses) in the receiver and it
is this that ensures that binary 0s and 1s originating at the
transmitter are correctly interpreted by the receiver; clearly, the
displacement of even one binary digit can cause havoc.

   A variety of synchronous protocols exist, such as the length of
block sent each time, the form of checking that takes place, the form
of acknowledgement, and so on. A synchronous protocol is not only a
function of the modem, which has to have a suitable clock, but also
of the software and firmware in the computers.  Because asynchronous
protocols transmit so many 'extra' bits in order to avoid error,
savings in transmission time under synchronous systems often exceed
20-30%. The disadvantage of synchronous protocols lie in increased
hardware costs.

   One other complication exists: most asynchronous protocols use the
ASCII code to define characters. IBM ('Big Blue'), the biggest
enthusiast of synchronous comms, has its own binary code to define
characters. In Appendix IV, you will find an explanation and a
comparison with ASCII.

** Page 13
   The hacker, wishing to come to terms with synchronous comms, has
two choices: the more expensive is to purchase a protocol convertor
board. These are principally available for the IBM PC, which has been
increasingly marketed for the 'executive workstation' audience, where
the ability to interface to a company's existing (IBM) mainframe is a
key feature. The alternative is to see whether the target mainframe
has a port on to a packet- switched service; in that event, the
hacker can use ordinary asynchronous equipment and protocols--the
local PAD (Packet Assembler/Disassembler) will carry out the
necessary transformations.


   Which brings us neatly to the world of high-speed digital networks
using packet-switching. All the computer communications so far
described have taken place either on the phone (voice-grade) network
or on the telex network.

   In Chapter 7 we will look at packet-switching and the
opportunities offered by international data networks. We must now
specify hackers' equipment in more detail.

** Page 14


Hackers' Equipment

   You can hack with almost any microcomputer capable of talking to
the outside world via a serial port and a modem. In fact, you don't
even need a micro; my first hack was with a perfectly ordinary
viewdata terminal.

   What follows in this chapter, therefore, is a description of the
elements of a system I like to think of as optimum for
straight-forward asynchronous ASCII and Baudot communications. What
is at issue is convenience as much as anything. With kit like this,
you will be able to get through most dial-up ports and into
packet-switching through a PAD -- a packet assembler/ disassembler
port. (It will not get you into IBM networks, because these use
different and incompatible protocols; we will return to the matter of
the IBM world in chapter 10.) In other words, given a bit of money, a
bit of knowledge, a bit of help from friends and a bit of luck, what
is described here is the sort of equipment most hackers have at their

   You will find few products on the market labelled 'for hackers';
you must select those items that appear to have 'legitimate' but
interesting functions and see if they can be bent to the hacker's
purposes. The various sections within this chapter highlight the sort
of facilities you need; before lashing out on some new software or
hardware, try to get hold of as much publicity and documentation
material as possible to see how adaptable the products are. In a few
cases, it is worth looking at the second-hand market, particularly
for modems, cables and test equipment.

   Although it is by no means essential, an ability to solder a few
connections and scrabble among the circuit diagrams of 'official'
products often yield unexpectedly rewarding results.

The computer

   Almost any popular microcomputer will do; hacking does not call
upon enormous reserves of computer power. Nearly everything you hack
will come to you in alphanumeric form, not graphics.  The computer
you already have will almost certainly have the essential qualities.
However the very cheapest micros, like the ZX81, whilst usable,
require much more work on the part of the operator/hacker, and give
him far less in the way of instant facilities.

** Page 15

(In fact, as the ZX81 doesn't use ASCII internally, but a
Sinclair-developed variant; you will need a software or firmware fix
for that, before you even think of hooking it up to a modem.)

   Most professional data services assume the user is viewing on an
80-column screen; ideally the hacker's computer should be capable of
doing that as well, otherwise the display will be full of awkward
line breaks. Terminal emulator software (see below) can some- times
provide a 'fix'.

   One or two disc drives are pretty helpful, because you will want
to be able to save the results of your network adventures as quickly
and efficiently as possible. Most terminal emulators use the
computer's free memory (i.e. all that is not required to support the
operating system and the emulator software itself) as store for the
received data, but once the buffer is full, you will begin to lose
the earliest items. You can, of course, try to save to cassette, but
normally that is a slow and tedious process.

   An alternative storage method is to save to a printer, printing
the received data stream not only to the computer screen, but also on
a dot matrix printer. However, most of the more popular (and cheaper)
printers do not work sufficiently fast. You may find you lose
characters at the beginning of each line. Moreover, if you print
everything in real-time, you'll include all your mistakes, false
starts etc., and in the process use masses of paper. So, if you can
save to disc regularly, you can review each hack afterwards at your
leisure and, using a screen editor or word processor, save or print
out only those items of real interest.

Serial ports

   The computer must have a serial port, either called that or marked
RS232C (or its slight variant RS423), or V24, which is the official
designator of RS232C used outside the USA, though not often seen on

   The very cheapest micros, like the ZX81, Spectrum, VIC20, do not
have RS232C ports, though add-on boards are available. Some of the
older personal computers, like the Apple or the original Pet, were
also originally sold without serial ports, though standard boards are
available for all of these.

   You are probably aware that the RS232C standard has a large number
of variants, and that not all computers (or add-on boards) that claim
to have a RS232C port can actually talk into a modem.

   Historically, RS232C/V24 is supposed to cover all aspects of
serial communication, including printers and dumb terminals as well
as computers. The RS232C standard specifies electrical and physical

** Page 16

   Everything is pumped through a 25-pin D-shaped connector, each pin
of which has some function in some implementation. But in most cases,
nearly all the pins are not used. In practice, only three connections
are essential for computer to modem communication:

Pin 7 signal ground

Pin 2 characters leaving the computer

Pin 3 characters arriving at the computer

   The remaining connections are for such purposes as feeding power
to an external device, switching the external advice on or off,
exchanging status and timing signals, monitoring the state of the
line, and so forth. Some computers and their associated firmware
require one or other of these status signals to go 'high' or 'low' in
particular circumstances, or the program hangs. Check your
documentation if you have trouble.

   Some RS232C implementations on microcomputers or add-on boards are
there simply to support printers with serial interfaces, but they can
often be modified to talk into modems. The critical two lines are
those serving Pins 2 and 3.

   A computer serving a modem needs a cable in which Pin 2 on the
computer is linked to Pin 2 on the modem.

   A computer serving a printer, etc, needs a cable in which Pin 3 on
the: computer is linked to Pin 2 on the printer and Pin 3 on the
printer is linked to Pin 2 on the computer.

   If two computers are linked together directly, without a modem,
then Pin 2 on computer A must be linked to Pin 3 on computer B and
Pin 3 on computer B linked to Pin 2 on computer A: this arrangement
is sometimes called a 'null modem' or a 'null modem cable'.

   There are historic explanations for these arrangements, depending
on who you think is sending and who is receiving--forget about them,
they are confusing. The above three cases are all you need to know
about in practice.

   One difficulty that frequently arises with newer or portable
computers is that some manufacturers have abandoned the traditional
25-way D-connector, largely on the grounds of bulk, cost and
redundancy. Some European computer and peripheral companies favour
connectors based on the DIN series (invented in Germany), while
others use D-connectors with fewer pin-outs.

** Page 17

   There is no standardisation. Even if you see two physically
similar connectors on two devices, regard them with suspicion. In
each case, you must determine the equivalents of:

Characters leaving computer (Pin 2)
Characters arriving at computer (Pin 3)
Signal ground (Pin 7)

   You can usually set the speed of the port from the computer's
operating system and/or from Basic. There is no standard way of doing
this; you must check your handbook and manuals. Most RS232C ports can
handle the following speeds:

75, 110, 300, 600, 1200, 2400, 4800, 9600

and sometimes 50 and 19200 baud as well. These speeds are selectable
in hardware by appropriate wiring of a chip called a baud-rate
generator. Many modern computers let you select speed in hardware by
means of a DIL switch.  The higher speeds are used either for driving
printers or for direct computer-to-computer or computer-to-peripheral
connections. The normal maximum speed for transmitting along phone
lines is 1200 baud.

   Depending on how your computer has been set up, you may be able to
control the speed from the keyboard--a bit of firmware in the
computer will accept micro-instructions to flip transistor switches
controlling the wiring of the baud-rate generator.  Alternatively,
the speeds may be set in pure software, the micro deciding at what
speed to feed information into the serial port.

   In most popular micro implementations the RS232C cannot support
split-speed working (different speeds for receive and transmit). If
you set the port up for 1200 baud, it has to be 1200 receive and
transmit. This is a nuisance in Europe, where 75/1200 is in common
use both for viewdata systems and for some on-line services. The
usual way round is to have special terminal emulator software, which
requires the RS232C hardware to operate at 1200 /1200 and then slows
down (usually the micro's transmit path) to 75 baud in software by
means of a timing loop. An alternative method relies on a special
modem, which accepts data from the computer at 1200/1200 and then
performs the slowing-down to 75 baud in its own internal firmware.

Terminal emulators

   We all need a quest in life. Sometimes I think mine is to search
for the perfect software package to make micros talk to the outside

** Page 18

   As in all such quests, the goal is occasionally approached but
never reached, if only because the process of the quest causes one to
redefine what one is looking for.

   These items of software are sometimes called communications
packages, or asynchronous comms packages, and sometimes terminal
emulators, on the grounds that the software can make the micro appear
to be a variety of different computer terminals. Until recently, most
on-line computer services assumed that they were being examined
through 'dumb' terminals--simply a keyboard and a screen, with no
attendant processing or storage power (except perhaps a printer).
With the arrival of PCs all this is slowly changing, so that the
remote computer has to do no more than provide relatively raw data
and all the formatting and on-screen presentation is done by the
user's own computer.  Terminal emulator software is a sort of
half-way house between 'dumb' terminals and PCs with considerable
local processing power.

   Given the habit of manufacturers of mainframe and mini- computers
to make their products as incompatible with those of their
competitors as possible (to maximise their profits), many slight
variants on the 'dumb' computer terminal exist--hence the
availability of terminal emulators to provide, in one software
package, a way of mimicking all the popular types.

   Basic software to get a computer to talk through its RS232C port,
and to take in data sent to it, is trivial. What the hacker needs is
software that will make his computer assume a number of different
personalities upon command, store data as it is collected, and print
it out.

   Two philosophies of presenting such software to the user exist:
first, one which gives the naive user a simple menu which says, in
effect, 'press a key to connect to database' and then performs
everything smoothly, without distracting menus. Such programs need an
'install' procedure, which requires some knowledge, but most
'ordinary' users never see this. Normally, this is a philosophy of
software writing I very much admire: however, as a hacker you will
want the precise opposite. The second approach to terminal emulator
software allows you to re configure your computer as you go on--there
is plenty of on-screen help in the form of menus allowing you to turn
on and off local echo, set parity bits, show non-visible control
codes and so on. In a typical hack, you may have only vague
information about the target computer, and much of the fun is seeing
how quickly you can work out what the remote computer wants to 'see'
- and how to make your machine respond.

** Page 19

   Given the numbers of popular computers on the market, and the
numbers of terminal emulators for each one, it is difficult to make a
series of specific recommendations. What follows there- fore, is a
list of the sort of facilities you should look for:

   On-line help You must be able to change the software
characteristics while on-line--no separate 'install' routine. You
should be able to call up 'help' menus instantly, with simple
commands --while holding on to the line.

Text buffer - The received data should be capable of going into the
computer's free memory automatically so that you can view it later
off-line. The size of the buffer will depend on the amount of memory
left after the computer has used up the space required for its
operating system and the terminal software.  If the terminal software
includes special graphics, as in Apple Visiterm or some of the ROM
packs used with the BBC, the buffer space may be relatively small.
The software should tell you how much buffer space you have used and
how much is left, at any time. A useful adjunct is an auto-save
facility which, when the buffer becomes full, stops the stream of
text from the host computer and automatically saves the buffer text
to disc. A number of associated software commands should let you turn
on and off the buffer store, clear it or, when off-line, view the
buffer. You should also be able to print the buffer to a 'line'
printer (dot-matrix or daisy wheel or thermal image).  Some terminal
emulators even include a simple line editor, so that you can delete
or adjust the buffer before printing. (I use a terminal emulator
which saves text files in a form which can be accessed by my
word-processor and use that before printing out.)

Half/full Duplex (Echo On/Off) - Most remote services use an echoing
protocol: this means that when the user sends a character to the host
computer, the host immediately sends back the same character to the
user's computer, by way of confirmation. What the user sees on his
computer screen, therefore, has been generated, not locally by his
direct action on the keyboard, but remotely by the host computer.
(One effect of this is that there may sometimes be a perceptible
delay between keystroke and display of a letter, particularly if you
are using a packet-switched connection--if the telephone line is
noisy, the display may appear corrupt). This echoing protocol is
known as full duplex, because both the user's computer and the host
are in communication simultaneously.

   However, use of full duplex/echo is not universal, and all
terminal emulators allow you to switch on and off the facility. If,
for example, you are talking into a half-duplex system (i.e. no
echo), your screen would appear totally blank. In these
circumstances, it is best if your software reproduces on the screen
your keystrokes.

** Page 20

However, if you have your computer set for half-duplex and the host
computer is actually operating in full duplex. each letter will
appear twice--once from the keyboard and once, echoing from the host,
ggiiwiinngg tthhiiss ssoorrtt ooff eeffffeecctt. Your terminal
emulator needs to able to toggle between the two states.

Data Format/Parity Setting - In a typical asynchronous protocol, each
character is surrounded by bits to show when it starts, when it ends,
and to signify whether a checksum performed on its binary equivalent
comes out even or odd.  The character itself is described, typically,
in 7 bits and the other bits, start, stop and parity, bringing the
number up to 10. (See chapter 2.) However, this is merely one very
common form, and many systems use subtle variants -- the ideal
terminal emulator software will let you try out these variants while
you are still on line. Typical variants should include:

              Word length    Parity    No stop bits

                     7       Even            2
                     7        Odd               2
                     7        Even            1
                     7        Odd               1
                     8        None            2
                     8        None            1
                     8        Even            1
                     8        Odd               1

(NB although the ASCII character set is 7 bit, 8 bits are sometimes
transmitted with a ~padding~ bit; machine code instructions for 8-bit
and 16-bit machines obviously need 8-bit transmissions.)

Show Control Characters - This is a software switch to display
characters not normally part of the text that is meant to be read but
which nevertheless are sent by the host computer to carry out display
functions, operate protocols, etc. With the switch on, you will see
line feeds displayed as ^J, a back-space as ^H and so on; see
Appendix IV for the usual equivalents.

   Using this device properly you will be able, if you are unable to
get the text stream to display properly on your screen, to work out
what exactly is being sent from the host, and modify your local
software accordingly.

** Page 21

Control-Show is also useful for spotting 'funnies' in passwords and
log-on procedures--a common trick is to include ^H (backspace) in the
middle of a log-on so that part of the full password is overwritten.
(For normal reading of text, you have Control-Show switched off, as
it makes normal reading difficult.)

Macros - This is the US term, now rapidly being adopted in the UK,
for the preformatting of a log-on procedure, passwords etc. Typical
connecting procedures to US services like The Source, CompuServe, Dow
Jones etc are relatively complicated, compared with using a local
hobbyist bulletin board or calling up Prestel. Typically, the user
must first connect to a packet- switched service like Telenet or
Tymnet (the US commercial equivalents of BT's PSS), specify an
'address' for the host required (a long string of letters and
numbers) and then, when the desired service or 'host' is on line,
enter password(s) to be fully admitted. The password itself may be in
several parts.

   The value of the 'macro' is that you can type all this junk in
once and then send off the entire stream any time you wish by means
of a simple command. Most terminal emulators that have this feature
allow you to preformat several such macros.

   From the hacker's point of view, the best type of macro facility
is one that can be itself addressed and altered in software:
supposing you have only part of a password: write a little routine
which successively tries all the unknowns; you can then let the
computer attempt penetration automatically. (You'll have to read the
emulator's manual carefully to see if it has software-addressable
macros: the only people who need them are hackers, and, as we have
often observed, very few out-and-out hacker products exist!)

Auto-dial - Some modems contain programmable auto-diallers so that
frequently-called services can be dialled from a single keyboard

   Again the advantage to the hacker is obvious--a partly- known
telephone number can be located by writing some simple software
routine to test the variables.

   However, not all auto-dial facilities are equally useful. Some
included in US-originated communications software and terminal
emulators are for specific 'smart' modems not available
elsewhere--and there is no way of altering the software to work with
other equipment. In general, each modem that contains an auto-dialler
has its own way of requiring instructions to be sent to it. If an
auto-dialling facility is important to you, check that your software
is configurable to your choice of auto-dial modem.

   Another hazard is that certain auto-diallers only operate on the
multi-frequency tones method ('touch-tone') of dialling used in large
parts of the United States and only very slowly being introduced in
other countries. The system widely used in the UK is called 'pulse'
dialling. Touch-tone dialling is much more rapid than pulse dialling,
of course.

** Page 22

   Finally, on the subject of US-originated software, some packages
will only accept phone numbers in the standard North American format
of: 3-digit area code, 3-digit local code, 4-digit subscriber code.
In the UK and Europe the phone number formats vary quite
considerably.  Make sure that any auto-dial facility you use actually
operates on your phone system.

Format Screen - Most professional on-line and time-share services
assume an 80-column screen. The 'format screen' option in terminal
emulators may allow you to change the regular text display on your
micro to show 80 characters across by means of a graphics 'fiddle';
alternatively, it may give you a more readable display of the stream
from the host by forcing line feeds at convenient intervals, just
before the stream reaches the right- hand margin of the micro's
'natural' screen width.

   Related to this are settings to handle the presentation of the
cursor and to determine cursor movement about the screen-- normally
you won't need to use these facilities, but they may help you when
on-line to some odd-ball, non-standard service.  Certain specific
'dumb' terminals like the VT52 (which has become something of a
mainframe industry standard) use special sequences to move the cursor
about the screen--useful when the operator is filling in standard
forms of information.

   Other settings within this category may allow you to view
characters on your screen which are not part of the normal character
set. The early Apples, for example, lacked lower case, presenting
everything in capitals (as does the ZX81), so various ingenious
'fixes' were needed to cope. Even quite advanced home computers may
lack some of the full ASCII character set, such oddities as the tilde
~ or backslash \ or curly bracket { }, for example.

Re-assign - keyboard A related problem is that home micro keyboards
may not be able to generate all the required characters the remote
service wishes to see.  The normal way to generate an ASCII character
not available from the keyboard is from Basic, by using a Print
CHR$(n) type command. This may not be possible when on-line to a
remote computer, where everything is needed in immediate mode. Hence
the requirement for a software facility to re-assign any little-used
key to send the desired 'missing' feature. Typical requirements are
BREAK~ ESC, RETURN (when part of a string as opposed to being the end
of a command) etc. When re-assigning a series of keys, you must make
sure you don't interfere with the essential functioning of the
terminal emulator.

** Page 23

For example, if you designate the sequence ctrl-S to mean 'send a DC1
character to the host', the chances are you will stop the host from
sending anything to you, because ctrl-S is a common command (some-
times called XOF) to call for a pause--incidentally, you can end the
pause by hitting ctrl-Q.  Appendix IV gives a list of the full ASCII
implementation and the usual 'special' codes as they apply to
computer-to-computer communications.

File Protocols - When computers are sending large files to each
other, a further layer of protocol, beyond that defining individual
letters, is necessary. For example, if your computer is automatically
saving to disk at regular intervals as the buffer fills up, it is
necessary to be able to tell the host to stop sending for a period,
until the save is complete. On older time-share services, where the
typical terminal is a teletypewriter, the terminal is in constant
danger of being unable mechanically to keep up with the host
computer's output. For this reason, many host computers use one of
two well-known protocols which require the regular exchange of
special control characters for host and user to tell each other all
is well. The two protocols are:

Stop/Start - The receiving computer can at any time send to the host
a Stop (ctrl-S) signal, followed by, when it is ready a Start,

EOB/ACK - The sending computer divides its file into a blocks (of any
convenient length); after each block is sent, an EOB (End of Block)
character is sent (see ASCII table, Appendix IV). The user's computer
must then respond with a ACK (Acknowledge) character.

   These protocols can be used individually, together or not at all.
You may be able to use the 'Show Control Codes' option to check
whether either of the protocols are in use. Alternatively, if you
have hooked on to a service which for no apparent reason, seems to
stop in its tracks, you could try ending an ACK or Start (ctrl-F or
ctrl-S) and see if you can get things moving.

File transmission - All terminal emulators assume you will want to
send, as well as receive, text files. Thus, in addition to the
protocol settings already mentioned, there may be additional ones for
that purpose, e.g. the XMODEM protocol very popular on bulletin
boards. Hackers, of course, usually don't want to place files on
remote computers.....

Specific terminal emulation - Some software has pre-formatted sets of
characteristics to mimic popular commercial 'dumb' terminals. For
example, with a ROM costing under 60 fitted to a BBC micro, you can
obtain almost all of the features of DEC's VT100 terminal, which
until recently was regarded as something of an industry-standard and
costing just under 1000.

** Page 24

Other popular terminals are the VT52 and some Tektronix models, the
latter for graphics display. ANSI have produced a 'standard'

Baudot characters - The Baudot code, or International Telegraphic
Code No 2, is the 5-bit code used in telex and telegraphy -- and in
many wire-based news services. A few terminal emulators include it as
an option, and it is useful if you are attempting to hack such
services. Most software intended for use on radio link-ups (see
Chapter 10) operates primarily in Baudot, with ASCII as an option.

Viewdata emulation - This gives you the full, or almost full,
graphics and text characters of UK-standard viewdata. Viewdata tv
sets and adapters use a special character-generator chip and a few,
mostly British-manufactured, micros use that chip also-- the Acorn
Atom was one example. The BBC has a teletext mode which adopts the
same display. But for most micros, viewdata emulation is a matter of
using hi-res graphics to mimic the qualities of the real thing, or to
strip out most of the graphics.  Viewdata works on a screen 40
characters by 24 rows, and as some popular home micros have 'native'
displays smaller than that, some considerable fiddling is necessary
to get them to handle viewdata at all.

   In some emulators, the option is referred to as Prestel or
Micronet--they are all the same thing. Micronet-type software usually
has additional facilities for fetching down telesoftware programs
(see Chapter 10).

   Viewdata emulators must attend not only to the graphics
presentation, but also to split-speed operation: the usual speeds are
1200 receive from host, 75 transmit to host. USA users of such
services may get them via a packet-switched network, in which case
they will receive it either at 1200/1200 full duplex or at 300/300.

   Integrated terminal emulators offering both 'ordinary'
asynchronous emulation and viewdata emulation are rare: I have to use
completely different and non-compatible bits of software on my own
home set-up.


   Every account of what a modem is and does begins with the classic
explanation of the derivation of the term: let this be no exception.
Modem is a contraction of modulator-demodulator.

A modem taking instructions from a computer (pin 2 on RS232C)
converts the binary 0's and 1's into specific single tones, according
to which 'standard' is being used. In RS232C/V24, binary 0 (ON)
appears as positive volts and binary 1 (OFF) appears as negative

** Page 25

The tones are then fed, either acoustically via the telephone
mouth-piece into the telephone line, or electrically, by generating
the electrical equivalent direct onto the line. This is the
modulating process.

   In the demodulating stage, the equipment sits on the phone line
listening for occurrences of pre-selected tones (again according to
whichever 'standard' is in operation) and, when it hears one,
delivers a binary 0 or binary 1 in the form of positive or negative
voltage pulses into pin 3 of the computer's serial port.

   This explanation holds true for modems operating at up to 1200
baud; above this speed, the modem must be able to originate tones,
and detect them according to phase as well, but since higher-speed
working is unusual in dial-up ports--the hacker's special interest,
we can leave this matter to one side.

   The modem is a relatively simple bit of kit: on the transmit side
it consists of a series of oscillators acting as tone generators, and
on receive has a series of narrow band-pass filters. Designers of
modems must ensure that unwanted tones do not leak into the telephone
line (exchanges and amplifiers used by telephone companies are
sometimes remotely controlled by the injection of specific tones) and
also that, on the receive side, only the distinct tones used for
communications are 'interpreted' into binary 0s or 1s. The other
engineering requirements are that unwanted electrical currents do not
wander down the telephone cable (to the possible risk of phone
company employees) or back into the user's computer.

   Until relatively recently, the only UK source of low-speed modems
was British Telecom. The situation is much easier now, but
de-regulation of 'telephone line attachments', which include modems,
is still so recent that the ordinary customer can easily become
confused. Moreover, modems offering exactly the same service can vary
in price by over 300%.  Strictly speaking, all modems connected to
the phone line should be officially approved by BT or other
appropriate regulatory authority.

   At 300 baud, you have the option of using direct-connect modems
which are hard-wired into the telephone line, an easy enough
exercise, or using an acoustic coupler in which you place the
telephone hand-set. Acoustic couplers are inherently prone to
interference from room-noise, but are useful for quick lash-ups and
portable operation. Many acoustic couplers operate only in
'originate' mode, not in' answer'. Newer commercial direct- connect
modems are cheaper than acoustic couplers.

** Page 26

   At higher speeds acoustic coupling is not recommended, though a
75/1200 acoustic coupler produced in association with the Prestel
Micronet service is not too bad, and is now exchanged on the
second-hand market very cheaply indeed.

   I prefer modems that have proper status lights--power on, line
seized, transmit and receive indicators. Hackers need to know what is
going on more than most users.

   The table below shows all but two of the types of service you are
likely to come across; V-designators are the world-wide 'official'
names given by the CCITT; Bell-designators are the US names:

Service        Speed  Duplex  Transmit    Receive     Answer
Designator                    0    1      0     1

V21 orig       300(*) full    1180  980   1850  1650   -
V21 ans        300(*) full    1850 1650   1180   980  2100
V23 (1)        600    half    1700 1300   1700  1300  2100
V23 (2)       1200    f/h(**) 2100 1300   2100  1300  2100
V23 back        75    f/h(**)  450  390    450   390   -
Bell 103 orig  300(*) full    1070 1270   2025  2225   -
Bell 103 ans   300(*) full    2025 2225   1070  1270  2225
Bell 202      1200    half    2200 1200   2200  1200  2025

(*)any speed up to 300 baud, can also include 75 and 110 baud

(**)service can either be half-duplex at 1200 baud or asymmetrical
full duplex, with 75 baud originate and 1200 baud receive (commonly
used as viewdata user) or 1200 transmit and 75 receive (viewdata

The two exceptions are:
V22 1200 baud full duplex, two wire
Bell 212A The US equivalent
These services use phase modulation as well as tone.

   British Telecom markets the UK services under the name of
Datel--details are given in Appendix V.

   BT's methods of connecting modems to the line are either to
hard-wire the junction box (the two outer-wires are the ones you
usually need)--a 4-ring plug and associated socket (type 95A) for
most modems, a 5-ring plug and associated socket (type 96A) for
Prestel applications (note that the fifth ring isn't used)--and, for
all new equipment, a modular jack called type 600. The US also has a
modular jack, but of course it is not compatible.

** Page 27

   Modern modem design is greatly aided by a wonder chip called the
AMD 7910.  This contains nearly all the facilities to modulate and
demodulate the tones associated with the popular speed services, both
in the CCITT and Bell standards. The only omission--not always made
clear in the advertisements--are services using 1200/1200
full-duplex, ie V22 and Bell 212A.

   Building a modem is now largely a question of adding a few
peripheral components, some switches and indicator lights, and a box.
In deciding which 'world standard' modem to purchase, hackers should
consider the following features:

Status lights you need to be able to see what is happening on the

Hardware/software switching - cheaper versions merely give you a
switch on the front enabling you to change speeds, originate or
answer mode and CClTT or Bell tones. More expensive ones feature
firmware which allows your computer to send specially formatted
instructions to change speed under program control.  However, to make
full use of this facility, you may need to write (or modify) your
terminal emulator.

Auto-dial - a pulse dialler and associated firmware are included in
some more expensive models. You should ascertain whether the
auto-dialer operates on the telephone system you intend to hook the
modem up to--some of the US 'smart' modems present difficulties
outside the States. You will of course need software in your micro to
address the firmware in the modem --and the software has to be part
of your terminal emulator, otherwise you gain nothing in convenience.
However, with appropriate software, you can get your computer to try
a whole bank of numbers one after the other.

D25 connector - this is the official 'approved' RS232CN24 physical
connection--useful from the point-of-view of easy hook-up. A number
of lower-cost models substitute alternative DIN connectors. You must
be prepared to solder up your own cables to be sure of connecting up

Documentation I always prefer items to be accompanied by proper
instructions.  Since hackers tend to want to use equipment in
unorthodox ways, they should look for good documentation too.

** Page 28

   Finally, a word on build-your-own modems. A number of popular
electronics magazines and mail-order houses have offered modem
designs. Such modems are not likely to be approved for direct
connection to the public telephone network. However, most of them
work. If you are uncertain of your kit-constructing skills, though.
remember badly-built modems can be dangerous both to your computer
and to the telephone network.

Test Equipment

   Various items of useful test equipment occasionally appear on the
second-hand market--via mail-order, in computer junk shops, in the
flea-market section of exhibitions and via computer clubs.

   It's worth searching out a cable 'break-out' box. This lets you
restrap a RS232C cable without using a soldering iron--the various
lines are brought out on to an accessible matrix and you use small
connectors to make (or break) the links you require.  It's useful if
you have an 'unknown' modem, or an unusually configured computer.

   Related, but much more expensive, is a RS232C/V24 analyser --this
gives LED status lights for each of the important lines, so you can
see what is happening.

   Lastly, if you are a very rich and enthusiastic hacker, you can
buy a protocol analyser. This is usually a portable device with a
VDU, full keyboard, and some very clever firmware which examines the
telephone line or RS232C port and carries out tests to see which of
several popular datacomms protocols is in use.  Hewlett Packard do a
nice range. Protocol analysers will handle synchronous transmissions
as well as synchronous. Cost: 1500 and up...and up.

** Page 29



   Wherever hackers gather, talk soon moves from past achievements
and adventures to speculation about what new territory might be
explored. It says much about the compartmentalisation of computer
specialities in general and the isolation of micro- owners from
mainstream activities in particular that a great deal of this
discussion is like that of navigators in the days before Columbus:
the charts are unreliable, full of blank spaces and confounded with

   In this chapter I am attempting to provide a series of notes on
the main types of services potentially available on dial-up, and to
give some idea of the sorts of protocols and conventions employed.
The idea is to give voyagers an outline atlas of what is interesting
and possible, and what is not.

On-line hosts

   On-line services were the first form of electronic publishing: a
series of big storage computers--and on occasion, associated
dedicated networks -- act as hosts to a group of individual databases
by providing not only mass data storage and the appropriate 'search
language' to access it, but also the means for registering, logging
and billing users. Typically, users access the on-line hosts via a
phone number which links into a a public data network using packet
switching (there's more on these networks in chapter 7).

   The on-line business began almost by accident; large corporations
and institutions involved in complicated technological developments
found that their libraries simply couldn't keep track of the
publication of relevant new scientific papers, and decided to
maintain indices of the papers by name, author, subject-matter, and
so on, on computer. One of the first of these was the armaments and
aircraft company, Lockheed Corporation.

   In time the scope of these indices expanded and developed and
outsiders -- sub-contractors, research agencies, universities,
government employees, etc were granted access. Other organisations
with similar information-handling requirements asked if space could
be found on the computer for their needs.

** Page 30

Eventually Lockheed and others recognised the beginnings of a quite
separate business; in Lockheed's case it lead to the foundation of
Dialogue, which today acts as host and marketing agent for almost 300
separate databases.  Other on-line hosts include BRS (Bibliographic
Retrieval Services), Comshare (used for sophisticated financial
modelling), DataStar, Blaise (British Library) I P Sharp, and

   On-line services, particularly the older ones, are not especially
user-friendly by modern standards. They were set up at a time when
both core and storage memory was expensive, and the search languages
tend to be abbreviated and formal. Typically they are used, not by
the eventual customer for the information, but by professional
intermediaries--librarians and the like-- who have undertaken special
courses. Originally on-line hosts were accessed by dumb terminals,
usually teletypewriters like the Texas Whisperwriter portable with
built-in acoustic modem, rather than by VDUs. Today the trend is to
use 'front-end' intelligent software on an IBM PC which allows the
naive user to pose his/her questions informally while offline; the
software then redefines the information request into the formal
language of the on-line host (the user does not witness this process)
and then goes on-line via an auto-dial modem to extract the
information as swiftly and efficiently as possible.

   On-line services require the use of a whole series of passwords:
the usual NUI and NUA for PSS (see chapter 7), another to reach the
host, yet another for the specific information service required.
Charges are either for connect-time or per record retrieved, or
sometimes a combination.

   The categories of on-line service include bibliographic, which
merely indexes the existence of an article or book--you must then
find a physical copy to read; and source, which contains the article
or extract thereof. Full-text services not only contain the complete
article or book but will, if required, search the entire text (as
opposed to mere keywords) to locate the desired information.  An
example of this is LEXIS, a vast legal database which contains nearly
all important US and English law judgements, as well as statutes.

News Services

The vast majority of news services, even today, are not, in the
strictest sense, computer-based, although computers play an important
role in assembling the information and, depending on the nature of
the newspaper or radio or tv station receiving it, its subsequent

** Page 31

   The world's big press agencies--United Press, Associated Press,
Reuters, Agence France Presse, TASS, Xinhua, PAP, VoA -- use telex
techniques to broadcast their stories. Permanent leased telegraphy
lines exist between agencies and customers, and the technology is
pure telex: the 5-bit Baudot code (rather than ASCII) is adopted,
giving capital letters only, and 'mark' and space' are sent by
changing voltage conditions on the line rather than audio tones.
Speeds are 50 or 75 baud.

   The user cannot interrogate the agency in any way. The stories
come in a single stream which is collected on rolls of paper and then
used as per the contract between agency and subscriber.  To hack a
news agency line you will need to get physically near the appropriate
leased line, tap in by means of an inductive loop, and convert the
changing voltage levels (+80 volts on the line) into something your
RS232C port can handle. You will then need software to translate the
Baudot code into the ASCII which your computer can handle internally,
and display on screen or print to a file. The Baudot code is given in
Appendix IV.

   None of this is easy and will probably involve breaches of several
laws, including theft of copyright material! However a number of news
agencies also transmit services by radio, in which case the signals
can be hijacked with a short-wave receiver. Chapter 9 explains.

   Historic news, as opposed to the current stuff from agencies, is
now becoming available on-line. The New York Times, for example, has
long held its stories in an electronic 'morgue' or clippings library.
Initially this was for internal use, but for the last several years
it has been sold to outsiders, chiefly broadcasting stations and
large corporations. You can search for information by a combination
of keyword and date-range. The New York Times Information Bank is
available through several on-line hosts.

   As the world's great newspapers increasingly move to electronic
means of production--journalists working at VDUs, sub-editors
assembling pages and direct-input into photo-typesetters--the
additional cost to each newspaper of creating its own morgue is
relatively slight and we can expect to see many more commercial

   In the meantime, other publishing organisations have sought to
make available articles, extract or complete, from leading magazines
also. Two UK examples are Finsbury Data Services' Textline and
Datasolve's d Reporter, the latter including material from the BBC's
monitoring service, Associated Press, the Economist and the Guardian.
Textline is an abstract service, but World Reporter gives the full
text. In October 1984 it already held 500 million English words.

** Page 32

   In the US there is NEXIS, which shares resources with LEXIS; NEXIS
held 16 million full text articles at that same date. All these
services are expensive for casual use and are accessed by dial-up
using ordinary asynchronous protocols.

   Many electronic newsrooms also have dial-in ports for reporters
out on the job; depending on the system these ports not only allow
the reporter to transmit his or her story from a portable computer,
but may also (like Basys Newsfury used by Channel Four News) let them
see news agency tapes, read headlines and send electronic mail. Such
systems have been the subject of considerable hacker speculation.

Financial Services

   The financial world can afford more computer aids than any other
non-governmental sector. The vast potential profits that can be made
by trading huge blocks of currency, securities or commodities--and
the extraordinary advantages that a slight 'edge' in information can
bring--have meant that the City, Wall Street and the equivalents in
Hong Kong, Japan and major European capitals have been in the
forefront of getting the most from high-speed comms.

   Ten years ago the sole form of instant financial information was
the ticker tape--telegraphy technology delivering the latest share
price movements in a highly abbreviated form. As with its news
equivalents, these were broadcast services (and still are, for the
services still exist) sent along leased telegraph lines. The user
could only watch, and 'interrogation' consisted of back-tracking
along a tape of paper. Extel (Exchange Telegraph) continues to use
this technique, though it is gradually upgrading by using viewdata
and intelligent terminals.

   However, just over ten years ago Reuters put together the first
packages which gave some intelligence and 'questioning power' to the
end user. Each Reuters' Monitor is intelligent, containing (usually)
a DEC PDP-8 series mini and some firmware which accepts and selects
the stream of data from the host at the far end of the leased line,
marshalls interrogation requests and takes care of the local display.
Information is formatted in 'pages' rather like viewdata frames, but
without the colour. There is little point in eavesdropping into a
Reuters line unless you know what the terminal firmware does. Reuters
now face an aggressive rival in Telerate, and the fight is on to
deliver not only fast comprehensive prices services but international
screen-based dealing as well. The growth of Reuters and its rivals is
an illustration of technology creating markets--especially in
international currency--where none existed before.

** Page 33

   The first sophisticated Stock Exchange prices 'screens' used
modified closed circuit television technology. London had a system
called Market Price Display Service--MPDS--which consisted of a
number of tv displays of current prices services on different
'channels' which could be selected by the user. But London now uses
TOPIC, a leased line variant on viewdata technology, though with its
magazine-like arrangement and auto-screen refresh, it has as much in
common with teletext as Prestel. TOPIC carries about 2,500 of the
total 7,500 shares traded in London, plus selected analytical
material from brokers.  Datastream represents a much higher level of
sophistication: using its 40,000 plus pa terminals you can compare
historic data-- price movements, movements against sector indices
etc--and chart the results.

   The hacker's reward for getting into such systems is that you can
see share and other prices on the move. None of these prices is
confidential; all could be obtained by ringing a stockbroker.
However, this situation is likely to change; as the City makes the
change from the traditional broker/jobber method of dealing towards
specialist market making, there will then be electronic prices
services giving privileged information to specialist share dealers.
All these services are only available via leased lines; City
professionals would not tolerate the delays and uncertainties of
dial-up facilities. However dial-up ports exist for demonstrations,
exhibitions, engineering and as back-up--and a lot of hacking effort
has gone into tracking them down.

   In the United States, in addition to Reuters, Telerate and local
equivalents of official streams of stock exchange and over-the-
counter data, there is Dow Jones, best known internationally for its
market indices similar to those produced by the Financial Times in
London. Dow Jones is in fact the owner of the Wall Street Journal and
some influential business magazines. Its Dow Jones News/Retrieval
Service is aimed at businesses and private investors. It features
current share prices, deliberately delayed by 15 minutes, historic
price data, which can be charted by the user's own computer
(typically an Apple or IBM PC) and historic 'morgue' type company
news and analysis. Extensions of the service enable customers to
examine accounts of companies in which they are interested. The bulk
of the information is US-based, but can be obtained world-wide via
packet-switching networks. All you need are the passwords and special

** Page 34

Business Information

   Business information is usually about the credit-worthiness of
companies, company annual reports, trading opportunities and market
research. The biggest electronic credit data resource is owned by the
international company Dun & Bradstreet: during 1985-86 it is due to
spend 25m on making its data available all over Europe, including
the UK. The service, which covers more than 250,000 UK businesses, is
called DunsPrint and access is both on-line and via a viewdata
front-end processor. Another credit agency, CNN Services, extensively
used already by the big clearing banks, and with 3000 customers
accessing information via viewdata sets, has recently also announced
an extended electronic retrieval service for its own called Guardian
Business Information A third UK credit service available
electronically is called InfoLink.

   In addition, all UK companies quoted on the London Stock Exchange
and many others of any size who are not, have a report and analysis
available from ICC (InterCompany Comparisons) who can be accessed via
on--line dial--up, through a viewdata interface and also by
Datastream customers. Dun & Bradstreet also have an on--line service
called KBE covering 20,000 key British enterprises.

   Prodigious quantities of credit and background data on US
companies can be found on several of the major on--line hosts. A
valid phone number, passwords and extracts from the operations manual
of one of the largest US services, TRW--it has credit histories on 90
million people--sat on some hackers' bulletin boards (of which much
more later) for over twelve months during 1983 and 1984 before the
company found out. No one knows how many times hackers accessed the
service. According to the Washington Post, the password and manual
had been obtained from a Sears Roebuck national chain store in
Sacramento; some hackers claimed they were able to alter credit
records, but TRW maintain that telephone access to their systems is
designed for read-only operations alone, updating of files taking
place solely on magnetic tape.

   US market research and risk analysis comes from Frost Sullivan.
Risk analysis tells international businessmen which countries are
politically or economically unstable, or likely t become so, and so
unsafe to do business with. I once found myself accessing a
viewdata-based international assessment service run b a company
called Control Risks, which reputedly has strong link to the Special
Air Service. As so often happens when hacker think they are about to
uncover secret knowledge, the actual data files seemed relatively
trivial, the sort of judgements that could be made by a bright sixth
former who read posh newspapers and thoughtful weekly magazines.

** Page 35

University facilities

   In complete contrast to computers that are used to store and
present data are those where the value is to deliver processing power
to the outside world.  Paramount among these are those installed in
universities and research institutes.

   Although hackers frequently acquire phone numbers to enter such
machines, what you can do once you are there varies enormously. There
are usually tiers and banks of passwords, each allowing only limited
access to the range of services. It takes considerable knowledge of
the machine's operating system to break through from one to another
and indeed, in some cases, the operating system is so thoroughly
embedded in the mainframe's hardware architecture that the
substantial modifications necessary to permit a hacker to roam free
can only be done from a few designated terminals, or by having
physical access to the machine. However, the hobbyist bulletin board
system quite often provides passwords giving access to games and the
ability to write and run programs in exotic languages--my own first
hands--on experience of Unix came in exactly this way. There are
bulletin boards on mainframes and even, in some cases, boards for

   Given the nature of hacking, it is not surprising that some of the
earliest japes occurred on computers owned by universities. Way back
in the 1970s, MIT was the location of the famous 'Cookie Monster',
inspired by a character in the then-popular Rowan & Martin Laugh-in
television show. As someone worked away at their terminal, the word
'cookie' would appear across their screen, at first slowly wiping out
the user's work. Unless the user moved quickly, things started to
speed up and the machine would flash urgently: "Cookie, cookie, give
me a cookie". The whole screen would pulse with this message until,
after a while, the hacking program relented and the 'Monster' would
clear the screen, leaving the message: "I didn't want a cookie
anyway." It would then disappear into the computer until it snared
another unsuspecting user. You could save yourself from the Monster
by typing the word "Cookie", to which it replied "Thank you" and then

   In another US case, this time in 1980, two kids in Chicago,
calling themselves System Cruncher and Vladimir, entered the computer
at DePaul University and caused a system crash which cost $22,000 to
fix. They were prosecuted, given probation and were then made a movie

** Page 36

   In the UK, many important university and research institution
computers have been linked together on a special data network called
SERCNET. SERC is the Science and Engineering Research Council.
Although most of the computers are individually accessible via PSS,
SERCNET makes it possible to enter one computer and pass through to
others. During early 1984, SERCNET was the target of much hacker
attention; a fuller account appears in chapter 7, but to anticipate a
little, a local entry node was discovered via one of the London
University college computers with a demonstration facility which, if
asked nicely, disgorged an operating manual and list of 'addresses'.
One of the minor joys of this list was an entry labelled "Gateway to
the Universe", pure Hitch-hiker material, concealing an extensive
long-term multi-function communications project. Eventually some
hackers based at a home counties university managed to discover ways
of roaming free around the network....


   Prominent among public fantasies about hackers is the one where
banks are entered electronically, accounts examined and some money
moved from one to another. The fantasies, bolstered by
under-researched low-budget movies and tv features, arise from
confusing the details of several actual happenings.

   Most 'remote stealing' from banks or illicit obtaining of account
details touch computers only incidentally and involve straight-
forward fraud, conning or bribery of bank employees. In fact, when
you think about the effort involved, human methods would be much more
cost-effective for the criminal. For hackers, however, the very
considerable effort that has been made to provide security makes the
systems a great challenge in them- selves.

   In the United Kingdom, the banking scene is dominated by a handful
of large companies with many branches.  Cheque clearing and account
maintenance are conducted under conditions of high security with
considerable isolation of key elements; inter-bank transactions in
the UK go through a scheme called CHAPS, Clearing House Automatic
Payments System, which uses the X.25 packet switching protocols (see
chapter 7). The network is based on Tandem machines; half of each
machine is common to the network and half unique to the bank. The
encryption standard used is the US Data Encryption Standard. Certain
parts of the network, relating to the en- and de-cryption of
messages, apparently auto-destruct if tampered with.

** Page 37

   The service started early in 1984.  The international equivalent
is SWIFT (Society for Worldwide Interbank Financial Transactions);
this is also X.25- based and it handles about half-a-million messages
a day.  If you want to learn someone's balance, the easiest and most
reliable way to obtain it is with a plausible call to the local
branch. If you want some easy money, steal a cheque book and cheque
card and practise signature imitation. Or, on a grander scale, follow
the example of the 780,000 kruggerand fraud in the City. Thieves
intercepted a telephone call from a solicitor or bank manager to
'authenticate' forged drafts; the gold coins were then delivered to a
bogus company.

   In the United States, where federal law limits the size of an
individual bank's operations and in international banking, direct
attacks on banks has been much easier because the technology adopted
is much cruder and more use is made of public phone and telex lines.
One of the favourite techniques has been to send fake authorisations
for money transfers. This was the approach used against the Security
National Pacific Bank by Stanley Rifkin and a Russian diamond dealer
in Geneva. $10.2m moved from bank to bank across the United States
and beyond. Rifkin obtained code numbers used in the bilateral Test
Keys. The trick is to spot weaknesses in the cryptographic systems
used in such authorisations. The specifications for the systems
themselves are openly published; one computer security expert, Leslie
Goldberg, was recently able to take apart one scheme--proposed but
not actually implemented--and show that much of the 'key' that was
supposed to give high level cryptographic security was technically
redundant, and could be virtually ignored. A surprisingly full
account of his 'perfect' fraud appears in a 1980 issue of the journal
Computer Fraud and Security Bulletin.

   There are, however, a few areas where banking is becoming
vulnerable to the less mathematically literate hacker. A number of
international banks are offering their big corporation customers
special facilities so that their Treasury Departments (which ensure,
among other things, that any spare million dollars are not left doing
nothing over night but are earning short-term interest) can have
direct access to their account details via a PC on dial-up. Again,
telebanking is now available via Prestel and some of its overseas
imitators. Although such services use several layers of passwords to
validate transactions, if those passwords are mis-acquired, since no
signatures are involved, the bank account becomes vulnerable.

** Page 38

   Finally, the network of ATMs (hole-in-the-wall cash machines) is
expanding greatly. As mentioned early in this book, hackers have
identified a number of bugs in the machines. None of them,
incidentally, lead directly to fraud. These machines allow card-
holders to extract cash up to a finite limit each week (usually
100). The magnetic stripe contains the account number, validation
details of the owner's PIN (Personal Identity Number), usually 4
digits, and a record of how much cash has been drawn that week. The
ATM is usually off-line to the bank's main computer and only goes
on-line in two circumstances--first, during business hours, to
respond to a customer's 'balance request'; and second, outside
regular hours, to take into local memory lists of invalid cards which
should not be returned to the customer, and to dump out cheque book
and printed statement requests.

   Hackers have found ways of getting more than their cash limit each
week. The ATMs belonging to one clearing bank could be 'cheated' in
this way: you asked for your maximum amount and then, when the
transaction was almost completed, the ATM asked you 'Do you want
another transaction, Yes/No?' If you responded 'yes' you could then
ask for--and get--your credit limit again, and again, and again. The
weakness in the system was that the magnetic stripe was not
overwritten to show you had had a transaction till it was physically
ejected from the machine. This bug has now been fixed.

   A related but more bizarre bug resided for a while on the ATMs
used by that first bank's most obvious High Street rivals. In that
case, you had to first exhaust your week's limit. You then asked for
a further sum, say 75. The machine refused but asked if you wanted a
further transaction. Then, you slowly decremented the amounts you
were asking for by 5...70, 65, 60...and so on, down to 10. You then
told the ATM to cancel the last 5 transaction...and the machine gave
you the full 75. Some hackers firmly believe the bug was placed
there by the original software writer. This bug too has now been

   Neither of these quirks resulted in hackers 'winning' money from
the banks involved; the accounts were in every case, properly
debited. The only victory was to beat the system. For the future, I
note that the cost of magnetic stripe reader/writers which interface
to PCs is dropping to very low levels. I await the first inevitable
news reports.

Electronic Mail

Electronic mail services work by storing messages created by some
users until they are retrieved by their intended recipients.

** Page 39

   The ingredients of a typical system are: registration/logging on
facilities, storage, search and retrieval, networking, timing and
billing. Electronic mail is an easy add-on to most mainframe
installations, but in recent years various organisations have sought
to market services to individuals, companies and industries where
electronic mail was the main purpose of the system, not an add-on.

   The system software in widest use is that of ITI-Dialcom; it's the
one that runs Telecom Gold. Another successful package is that used
in the UK and USA by Easylink, which is supported by Cable & Wireless
and Western Union.

   In the Dialcom/Telecom Gold service, the assumption is made that
most users will want to concentrate on a relatively narrow range of
correspondents. Accordingly, the way it is sold is as a series of
systems, each run by a 'manager': someone within a company. The
'manager' is the only person who has direct contact with the
electronic mail owner and he in turn is responsible for bringing
individual users on to his 'system' -- he can issue 'mailboxes'
direct, determine tariff levels, put up general messages.  In most
other services, every user has a direct relationship with the
electronic mail company.

   The services vary according to their tariff structures and levels;
and also in the additional facilities: some offer bi-directional
interfaces to telex; and some contain electronic magazines, a little
like videotex.

   The basic systems tend to be quite robust and hacking is mainly
concentrated on second-guessing users IDs. Many of the systems have
now sought to increase security by insisting on passwords of a
certain length--and by giving users only three or four attempts at
logging on before closing down the line. But increasingly their
customers are using PCs and special software to automate logging-in.
The software packages of course have the IDs nicely pre-stored....

Government computers

   Among hackers themselves the richest source of fantasising
revolves around official computers like those used by the tax and
national insurance authorities, the police, armed forces and
intelligence agencies.

   The Pentagon was hacked in 1983 by a 19-year-old Los Angeles
student, Ronald Austin.  Because of the techniques he used, a full
account is given in the operating systems section of chapter 6. NASA,
the Space Agency, has also acknowledged that its e-mail system has
been breached and that messages and pictures of Kilroy were left as

** Page 40

   This leaves only one outstanding mega-target, Platform, the global
data network of 52 separate systems focused on the headquarters of
the US's electronic spooks, the National Security Agency at Fort
Meade, Maryland. The network includes at least one Cray-1, the worlds
most powerful number-cruncher, and facilities provided by GCHQ at

   Although I know UK phone freaks who claim to have managed to
appear on the internal exchanges used by Century House (M16) and
Curzon Street House (M15) and have wandered along AUTOVON, the US
secure military phone network, I am not aware of anyone bold or
clever enough to have penetrated the UK's most secure computers.

   It must be acknowledged that in general it is far easier to obtain
the information held on these machines--and lesser ones like the DVLC
(vehicle licensing) and PNC (Police National Computer)-- by criminal
means than by hacking -- bribery, trickery or blackmail, for example.
Nevertheless, there is an interesting hacker's exercise in
demonstrating how far it is possible to produce details from open
sources of these systems, even when the details are supposed to be
secret. But this relates to one of the hacker's own secret
weapons--thorough research, the subject of the next chapter.

** Page 41


Hackers' Intelligence

   Of all the features of hacking that mystify outsiders, the first
is how the hackers get the phone numbers that give access to the
computer systems, and the passwords that open the data. Of all the
ways in which hacking is portrayed in films, books and tv, the most
misleading is the concentration on the image of the solitary genius
bashing away at a keyboard trying to 'break in'.

   It is now time to reveal one of the dirty secrets of hacking:
there are really two sorts of hacker. For this purpose I will call
them the trivial and the dedicated. Anyone can become a trivial
hacker: you acquire, from someone else, a phone number and a password
to a system; you dial up, wait for the whistle, tap out the password,
browse around for a few minutes and log off.  You've had some fun,
perhaps, but you haven't really done anything except follow a
well-marked path. Most unauthorised computer invasions are actually
of this sort.

   The dedicated hacker, by contrast, makes his or her own
discoveries, or builds on those of other pioneers. The motto of
dedicated hackers is modified directly from a celebrated split
infinitive: to boldly pass where no man has hacked before.

   Successful hacking depends on good research. The materials of
research are all around: as well as direct hacker-oriented material
of the sort found on bulletin board systems and heard in quiet
corners during refreshment breaks at computer clubs, huge quantities
of useful literature are published daily by the marketing departments
of computer companies and given away to all comers: sheaves of
stationery and lorry loads of internal documentation containing
important clues are left around to be picked up. It is up to the
hacker to recognise this treasure for what it is, and to assemble it
in a form in which it can be used.

   Anyone who has ever done any intelligence work, not necessarily
for a government, but for a company, or who has worked as an
investigative journalist, will tell you that easily 90% of the
information you want is freely available and that the difficult part
is recognising and analysing it.  Of the remaining 10%, well over
half can usually be inferred from the material you already have,
because, given a desired objective, there are usually only a limited
number of sensible solutions.

** Page 42

You can go further: it is often possible to test your inferences and,
having done that, develop further hypotheses. So the dedicated
hacker, far from spending all the time staring at a VDU and 'trying
things' on the keyboard, is often to be found wandering around
exhibitions, attending demonstrations, picking up literature, talking
on the phone (voice-mode!) and scavenging in refuse bins.

   But for both trivial operator, and the dedicated hacker who wishes
to consult with his colleagues, the bulletin board movement has been
the single greatest source of intelligence.

Bulletin Boards

   Since 1980, when good software enabling solitary micro-computers
to offer a welcome to all callers first became widely available, the
bulletin board movement has grown by leaps and bounds. If you haven t
logged on to at least one already, now is the time to try. At the
very least it will test out your computer, modem and software --and
your skills in handling them. Current phone numbers, together with
system hours and comms protocol requirements, are regularly published
in computer mags; once you have got into one, you will usually find
current details of most of the others.

   Somewhere on most boards you will find a series of Special
Interest Group (SIG) sections and among these, often, will be a
Hacker's Club. Entrance to each SIG will be at the discretion of the
Sysop, the Bulletin Board owner. Since the BBS software allows the
Sysop to conceal from users the list of possible SIGs, it may not be
immediately obvious whether a Hacker's section exists on a particular
board. Often the Sysop will be anxious to form a view of a new
entrant before admitting him or her to a 'sensitive' area. It has
even been known for bulletin boards to carry two hacker sections:
one, admission to which can be fairly easily obtained; and a second,
the very existence of which is a tightly-controlled secret, where
mutually trusting initiates swap information.

   The first timer, reading through a hacker's bulletin board, will
find that it seems to consist of a series of discursive conversations
between friends.  Occasionally, someone may write up a summary for
more universal consumption.  You will see questions being posed. if
you feel you can contribute, do so, because the whole idea is that a
BBS is an information exchange. It is considered crass to appear on a
board and simply ask 'Got any good numbers?; if you do, you will not
get any answers. Any questions you ask should be highly specific,
show that you have already done some ground-work, and make clear that
any results derived from the help you receive will be reported back
to the board.

** Page 43

   Confidential notes to individuals, not for general consumption,
can be sent using the E-Mail option on the bulletin board, but
remember, nothing is hidden from the Sysop.

   A flavour of the type of material that can be seen on bulletin
boards appears from this slightly doctored excerpt (I have removed
some of the menu sequences in which the system asks what you want to
do next and have deleted the identities of individuals):

Msg#: 3538 *Modem Spot*
01/30/84 12:34:54 (Read 39 Times)
From: xxxxxxxxxx


Msg#: 3570 *Modem Spot*
01/31/84 23:43:08 (Read 31 Times)

Hsg#: 3662 *HACKER'S CLUB*
02/04/84 23:37:11 (Read 41 Times)
Does anyone know what the Public Data Net is? I appear to have access to it, &
I daren't ask what it is!
Also, can anyone tell me more about the Primenet systems... Again I seem to
have the means,but no info. For instance, I have a relative who logs on to
another Prime Both of our systems are on Primenet, is there any way we can
More info to those who want it...

<n>ext msg, <r>eply, or <s>top?
Msg has replies, read now(Y/N)? y

Reply has been deleted

<n>ext msg, <r>eply, or <s>top?

Msg#: 3739 *HACKER'S CLUB*
02/06/84 22:39:06 (Read 15 Times)
From: xxxxxxxxxx
To: xxxxxxxxxx
Ahh, but what is the significance of the Address-does it mean a PSS number. or
some thing like that? Meanwhile, I'II get on-line (via voice-link on the phone!)
to my cousin, and see what he has on it....

** Page 44

Msg#: 3766 *HACKER'S CLUB*
02/07/84 13:37:54 (Read 13 Times)
From: xxxxxxxxxxx
To: xxxxxxxxxxx
Primenet is a local network. I know of one in Poole, An BTGold use
one between their systems too. It Is only an internal network, I
suggest using PSS to communicate between different primes. Cheers.

<n>ext msg, <r>eply, or <s>top?

Msg#: 3799 *BBC*
02/07/84 22:09:05 (Read 4 Times)
From: xxxxxxxxxxx
To: xxxxxxxxxxx
The normal video output BNC can be made to produce colour video by
making a link near to the bnc socket on the pcb. details are in the
advanced user guide under the chapter on what the various links do.
If you require more I will try to help, as I have done this mod and
it works fine

Msg#: 935 *EREWHON*
09/25/83 01:23:00 (Read 90 Times)
From: xxxxxxxxxx
USA Phone Freaking is done with a 2 out of 5 Code. The tones must be
with 30Hz, and have less than 1% Distortion.

Master Tone Frequency = 2600 Hz.
>1 = 700 & 900 Hz
>2 = 700 & 1100 Hz
>3 = 900 & 1100 HZ
>4 = 700 & 1300 Hz
>5 = 900 & 1300 Hz
>6 = 1100 & 1300 Hz
>7 = 700 & 1500 HZ
>8 = 900 & 1500 Hz
>9 = 1100 & 1500 Hz
>0 = 1300 & 1500 Hz
>Start Key Signal = 1100 & 1700 Hz
>End Key Signal = 1300 & 1700 Hz
> Military Priority Keys 11=700 & 1700 ; 12=900 & 1700 - I don't
recommend using these. ( The method of use will be explained in a

Msg#: 936 *EREWHON*
09/20/83 01:34:43 (Read 89 Times)
From: xxxxxxxxxxxx

The UK System also uses a 2 out of 5 tone pattern.

The Master Frequency is 2280 Hz
>I = 1380 & 1500 Hz
>2 = 1380 & 1620 Hz
>3 = 1500 & 1620 Hz
>4 = 1380 & 1740 Hz
>5 = 1500 & 1740 Hz
>6 = 1620 & 1740 Hz
>7 = 1380 & I860 Hz
>8 = 1500 & 1860 Hz
>9 = 1620 & 1860 Hz
>0 = 1740 & 1860 Hz
>Start Key = 1740 & 1980 ; End Keying = 1860 & 1980 Hz
>Unused I think 11 = 1380 & 1980 ; 12 = 1500 & 1980 Hz

This is from the CCITT White Book Vol. 6 and is known as SSMF No. 3
to some B.T. Personnel.

The 2280 Hz tone is being filtered out at many exchanges so you may
need quite high level for it to work.

** Page 45

Msg#: 951 *EREWHON*
09/21/83 17:44:28 (Read 79 Times)
From: xxxxxxxxxx
In two other messages you will find the frequencies listed for the
Internal phone system controls. This note is intended to explain how
the system could be operated. The central feature to realise is that
( especially in the (USA) the routing information in a call is not in
the Dialled Code. The normal sequence of a call is that the Area Code
is received while the Subscriber No.  Is stored for a short period.
The Local Exchange reads the area code and selects the best route at
that time for the call. The call together with a new "INTERNAL"
dialling code Is then sent on to the next exchange together with the
subscriber number. This is repeated from area to area and group to
group.  The system this way provides many routes and corrects itself
for failures.

The Technique. make a Long Distance call to a number which does not
answer.  Send down the Master Tone. (2600 or 22080 Hz) This will
clear the line back, but leave you in the system. You may now send
the "Start key Pulse" followed by the Routing Code and the Subscriber
No. Finish with the "End keying Pulse". The system sees you as being
a distant exchange requesting a route for a call.

Meanwhile back at the home base. Your local exchange will be logging
you in as still ringing on the first call. There are further problems
in this in both the USA and the UK as the techniques are understood
and disapproved of by those in authority. You may need to have a
fairly strong signal into the system to get past filters present on
the line. Warning newer exchanges may link these filters to alarms.
Try from a phone box or a Public Place and see what happens or who

Example:- To call from within USA to Uk:
> Ring Toll Free 800 Number
> Send 2600 Hz Key Pulse
> When line goes dead you are in trunk level
> Start Pulse 182 End Pulse = White Plains N.Y. Gateway continued in
next message

Hsg#: 952 *EREWHON*
09/21/83 18:03:12 (Read 73 Times)
From: xxxxxxxxxx

> Start Pulse 044 = United Kingdom
> 1 = London ( Note no leading O please )
> 730 1234 = Harrods Department Store.

Any info on internal address codes would be appreciated from any

Msg#: 1028 *EREWHON*
09/25/83 23:02:35 (Read 94 Times)
From: xxxxxxxxxxxx

The following info comes from a leaflet entitled 'FREEFONE':

"British Telecom's recent record profits and continuing appalling
service have prompted the circulation of this information. It
comprises a method of making telephone calls free of charge."

Circuit Diagram:

O---o-------    -------o----O
:   !                  !    :
:   !                  !    :
L   o--------  --------o    P
I   !                  !    H
N   !                  !    O
E   o--    ------  ----o    N
:   !                  !    E
I   !                  !    :
N   o-------    -------o    :
:                           :
:                           :
:                           :

** Page 46

S1 = XXX
C1 = XXX
D1 = XXX
D2 = XXX
R1 = XXX


MSG#: 1029 *EREWHON*
09/25/83 23:19:17 (Read 87 Times)
From xxxxxxxxxxx

Circuit Operation:

The circuit inhibits the charging for incoming calls only. When a
phone is answered, there is normally approx. IOOmA DC loop current
but only 8mA or so is necessary to polarise the mic In the handset.
Drawing only this small amount is sufficient to fool BT's ancient
"Electric Meccano".

It's extremely simple. When ringing, the polarity of the line
reverses so D1 effectively answers the call when the handset is
lifted. When the call is established, the line polarity reverts and
R1 limits the loop current while D2 is a LED to indicate the circuit
is in operation. C1 ensures speech is unaffected. S1 returns the
telephone to normal.

Local calls of unlimited length can be made free of charge. Long
distance calls using this circuit are prone to automatic
disconnection this varies from area to area but you will get at least
3 minutes before the line is closed down.  Further experimentation
should bear fruit in this respect.

Sith the phone on the hook this circuit is completely undetectable.
The switch should be cLosed if a call is received from an operator,
for example, or to make an outgoing call. It has proved extremely
useful, particularly for friends phoning from pay phones with jammed
coin slots.

*Please DO NOT tell ANYONE where yoU found this information*

Msg#: 1194 *EREWHON*
10/07/83 04:50:34 (Read 81 Times)
From: xxxxxxxxxxxx

Free Test Numbers

Here are some no's that have been found to work:
Dial 174 <last 4 figs of your no>: this gives unobtainable then when
you replace handset the phone rings.

Dial 175 <last 4 figs of your no: this gives start test...start
then when you hang-up
the phone rings. pick it up and
either get dial tone which indicates ok or will a recording
i.e poor insulation b linetelling whats wrong. if can immediately 1305 to do further test
might say faulty pulsesother numbers try
are 182184
185.  i have discovered my exchange (pontybodkin) ring for 1267.

these all depend on local so pays experiment starting with 1
functions. discover something interest let me know sig.

msg: 2241 *erewhon*
12/04/83 20:48:49 (read 65 times)
from: sysop
to: serious freaks
subj: usa info

there is company (?) in called loopmaniacs unlimitedpo box 1197port townsend.wa98368 who publish books
telephone hacking.
some circuits even. write m. hoy there. one their publications steal book at s5.95 plus about $4
post. its worth stealing but dont show customs!** page 47

msg#: 3266
01/22/84 06:25:01 53 xxxxxxxxxx university
computers already described getting onto ucl pad allows various calls.
via network access many university/research full
list use
call 40 helpselect guide.
typing view prompt listing addresses. host be used by addrwhere
address. passwords demo etc. find anything interesting report here.
hint: aviod hanging end each
logon command - name pwd. seems
trick. another number: tel: (0235) 834531. data
exchange. bit harder wake up. must send break
level start. done using software maplin
just momentarily pull out rs232 com. returns. classes could manchesters help:- 1020300user:demo pwd:demo enre pacx. 3687 *hacker club*
02/05/84 14:41:43 416 xxxxxxxxxxxx hackers following collected sig:

commodore bbs (finland)       358 61 116223

gateway            01 600 1261
prestest (1200/75) 583 9412 useful prestel nodes 640..res.d (martlesham experiments
dynamic drcscept standardspicture601
(mailboxtelemessagingtelex link maybe telecom gold)651
(scratchpad -always changing). occasionally parts 650 (ip news) not properly cuged off. 190 sometimes well. boards specialised lonely hearts services ! an asterisk bell tones
*burbank ca213-840-8252213-842-9452
*la palma714-220-0239
*san francisco415-467-2588
*santa monica213-390-3239
*sherman oaks213-990-6830
*crystal rivers fl*atlantaga912-233-0863
*new yorkny212-541-5975
*newport newsva   804-838-3973
marseillesfrance 33-91-91-0060

both nos. prefix (0101)
a) daily x-rated doke service 516-922-9463
b) auto-biographies young ladies normally work
unpublishable magazines 212-976-2727.
c)dial wank0101 48 3688 14:44:51 393 xxxxxxxxxxx cont...
hertford pdp 11/70 bbs: 0707-263577 110 baud selected. type: set speed 300crafter hitting switch baud. hello 124
!password: hae4 ><cr>
When logged on type: COMMAND HACKER <cr>
Use: BYE to log out
EUCLID            388-2333
YOU CAN ALSO USE 01-278-4355.
unknown 300 Baud         01-854 2411
01-854 2499
Honeywell:From London dial the 75, else 0753(SLOUGH)
75 74199 75 76930
Type- TSS
User id: D01003
password: Unknown (up to 10 chars long)
Type: EXPL GAMES LIST to list games
To run a game type: FRN GAMES(NAME) E for a fotran game.
Replace FRN with BRN for BASIC games.
Central London Poly 01 637 7732/3/4/5
PSS (300)        0753 6141
Comshare (300)   01 351 2311
'Money Box'      01 828 9090
Imperial College 01 581 1366
01 581 1444
These are most of the interesting numbers that have come up over the
last bit. If I have omitted any, please leave them in a message.

Cheers, xxxxx.

Msg#: 5156 *HACKER'S CLUB*
04/15/84 08:01:11 (Read 221 Times)
From: xxxxxxxxxx
You can get into Datastream on dial-up at 300/300 on 251 6180 - no I
don't have any passwords....you can get into Inter Company
Comparisons (ICC) company database of 60,000 companies via their
1200/75 viewdata front-end processor on 253 8788. Type ***# when
asked for your company code to see a demo...

Msg#: 5195 *HACKER'S CLUB*
04/17/84 02:28:10 (Read 229 Times)
From: xxxxxxxxxx

** Page 49

Msg#: 7468 *EREWHON*
06/29/84 23:30:24 (Read 27 Times)
From: xxxxxxxxxx

Msg#: 7852 t*ACKER'S CLUB*
08/17/84 00:39:05 (Read 93 Times)
From: xxxxxxxxxx

Msg#:8154 *EREWHON*
08/02/84 21:46:11 (Read 13 Times)
From: ANON



JOLLY ROGER               713-468-0174 
PIRATE'S CHEST            617-981-1349 
PIRATE'S DATA CENTER      213-341-3962 
PIRATE'S SPACE STATION    617-244-8244 
PIRATE'S OUTHOUSE         301-299-3953 
PIRATE'S HANDLE           314-434-6187 
PIRATE'S DREAM            713-997-5067 
PIRATE'S TRADE            213-932-8294 
PIRATE'S TREK             914-634-1268 
PIRATE'S TREK III         914-835-3627 
PIRATE-80                 305-225-8059 
SANCTUARY                 201-891-9567 
SECRET SERVICE ][         215-855-7913 
SKELETON ISLAND           804-285-0041 
BOCA HARBOR               305-392-5924 
PIRATES OF PUGET SOUND    206-783-9798 
THE INSANITARIUM          609-234-6106 
HAUNTED MANSION           516-367-8172 
WASTELANDS                513-761-8250 
PIRATE'S HARBOR           617-720-3600 
SKULL ISLAND              203-972-1685 
THE TEMPLE                305-798-1615 
SIR LANCELOT'S CASTLE     914-381-2124 
PIRATE'8 CITY             703-780-0610 
PIRATE-S GALLEY           213-796-6602 
THE PAWN SHOPPE           213-859-2735 
HISSION CONTROL           301-983-8293 
BIG BLUE MONSTER          305-781-1683 
THE I.C.'S SOCKET         213-541-5607 
THE MAGIC REALM           212-767-9046 
PIRATE'S BAY              415-775-2384 
BEYOND BELIEF             213-377-6568 
PIRATE's TROVE            703-644-1665 
CHEYANNE MOUNTAIN         303-753 1554 
ALAHO CITY                512-623-6123 
CROWS NEST                617-862-7037 
PIRATE'S PUB ][           617-891-5793 
PIRATE'S I/0              201-543-6139 
SOUNDCHASER               804-788-0774 
SPLIT INFINITY            408-867-4455 
CAPTAIN'S LOG             612-377-7747 
THE SILHARILLION          714-535-7527 
TWILIGHT PHONE            313-775-1649 
THE UNDERGROUND           707-996-2427 
THE INTERFACE             213-477-4605 
THE DOC BOARD             713-471-4131 
SYSTEM SEVEN              415-232-7200 
SHADOW WORLD              713-777-8608 
OUTER LIMITS              213-784-0204 
METRO                     313-855-6321 
MAGUS                     703-471-0611 
GHOST SHIP 111 - PENTAGON 312-627-5138 
GHOST SHIP - TARDIS       312-528-1611 
DATA THIEVES              312-392-2403 
DANGER ISLAND             409-846-2900 
CORRUPT COMPUTING         313-453-9183 
THE ORACLE                305-475-9062 
PIRATE'S PLANET           901-756-0026 
CAESER S PALACE           305-253-9869 
CRASHER BBS               415-461-8215 
PIRATE'S BEACH            305-865-5432
PIRATE'S COVE             516-698-4008
PIRATE'S WAREHOUSE        415-924-8338
PIRATE'S PORT             512-345-3752
PIRATE'S NEWSTAND ][      213-373-3318
PIRATE'S GOLDMINE         617-443-7428
PIRATE'S SHIP             312-445-3883
PIRATE'S MOUNTAIN         213-472-4287
PIRATE'S TREK ][          914-967-2917
PIRATE'S TREK IV          714-932-1124
PORT OR THIEVES           305-798-1051
SECRET SERVICE            213-932-8294
SHERWOOD FOREST           212-896-6063
GALAXY ONE                215-224-0864
R.A.G.T.I.H.E.            217-429-6310
KINGDOM OF SEVEN          206-767-7777
THE STAR SYSTEM           516-698-7345
ALPHANET                  203-227-2987
HACKER HEAVEN             516-796-6454
PHANTOM ACCESS            814-868-1884
THE CONNECTION            516-487-1774
THE TAVERN                516-623-9004
PIRATE'S HIDEAWAY         617-449-2808
PIRATE'S PILLAGE          317-743-5789
THE PARADISE ON-LINE      512-477-2672
MAD BOARD FROM MARS       213-470-5912
NERVOUS SYSTEM            305-554-9332
DEVO                      305-652-9422
TORTURE CHAMBER           213-375-6137
HELL                      914-835-4919
CRASHER BBS               415-461-8215
ALCATRAZ                  301-881-0846
THE TRADING POST          504-291-4970
DEATH STAR                312-627-5138
THE CPU                   313-547-7903
TRADER'S INN              618-856-3321
PIRATE'S PUB              617-894-7266
BLUEBEARDS GALLEY         213-842-0227
MIDDLE EARTH              213-334-4323
EXIDY 2000                713-442-7644
SHERWOOD FOREST ][        914-352-6543
WARLOCK~S CASTLE          618-345-6638
TRON                      312-675-1819
THE SAFEHOUSE             612-724-7066
THE GRAPE VINE            612-454-6209
THE ARK                   701-343-6426
SPACE VOYAGE              713-530-5249
OXGATE                    804-898-7493
MINES OF MORIA ][         408-688-9629
MERLIN'S TOWER            914-381-2374
GREENTREE                 919-282-4205
GHOST SHIP ][ - ARAGORNS  312-644-5165
GENERAL HOSPITAL          201-992-9893
DARK REALM                713-333-2309
COSMIC VOYAGE             713-530-5249
CAMELOT                   312-357-8075
PIRATE'S GUILD            312-279-4399
HKGES                     305-676-5312
MINES OF MORIA            713-871-8577
A.S.C.I.I.                301-984-3772  

** Page 50

If Anybody is mad enough to actually dial up one (or more') of these
BBs please log everything so thAt others may benefit from your
efforts. IE- WE only have to register once, and we find out if this
board suits our interest.  Good luck and have fun! Cheers,

Msg#: 8163 *HACKER'S CLUB*
08/30/84 18:55:27 (Read 78 Times)
NBBS East is a relatively new bulletin board running from lOpm to
1230am on 0692 630610. There are now special facilities for BBC users
with colour, graphics etc. If you call it then please try to leave
some messages as more messages mean more callers, which in turn means
more messages Thanks a lot, Jon

Msg#: 8601 *HACKER'S CLUB*
09/17/84 10:52:43 (Read 57 Times!
From: xxxxxxxxxx
To: xxxxxxxxx
Subj: REPLY TO Msg# 8563 (HONEYWELL)
The thing is I still ( sort of I work for XXX so I don't think they
would be too pleased if I gave out numbers or anything else. and I
would rather keep my job Surely you don't mean MFI furniture ??

Msg#: 8683 *HACKER'S CLUB*
09/19/84 19:54:05 (Read 63 Times)
From: xxxxxxxxx
To those who have difficulty finding interesting numbers. try the UCL
Data Node on 01-388 2333   (300 baud).When you get the Which Service?
prompt. type PAD and a couple of CRs. Then, when the PAD> prompt
appears type CALL XOOXOOX, where is any(number orrange of numbers.
Indeed you can try several formats and numbers until you find
something interesting. The Merlin Cern computer is 9002003 And it's
difficult to trace You through aq data exchange! If anyone finds any
interesting numbers, let me know on this board, or Pretsel mailbox

Msg has replies, read now(Y/N)' Y

Msg#: 9457 *HACKER'S CLUB*
10/11/84 01:52:56 (Read 15 Times)
From:  xxxxxxxxxxx
To: xxxxxxxxxxx
ON 000 0000

Msg#: 8785 *HACKER'S CLUB*
09/21/B4 20-28-59 (Read 40 Times)
From xxxxxxxxxxxxxx
Subj: NEW Number

good LUCK!

** Page 51

   Please note that none of these hints, rumours, phone numbers and
passwords are likely to work by the time you are reading this...
However, in the case of the US credit agency TRW, described in the
previous chapter, valid phone numbers and passwords appear to have
sat openly on a number of bulletin boards for up to a year before the
agency realised it. Some university mainframes have hacker's boards
hidden on them as well.

   It is probably bad taste to mention it, but of course people try
to hack bulletin boards as well. An early version of one of the most
popular packages could be hacked simply by sending two semi-colons
(;;) when asked for your name. The system allowed you to become the
Sysop, even though you were sitting at a different computer; you
could access the user file, complete with all passwords, validate or
devalidate whomever you liked, destroy mail, write general notices,
and create whole new areas...

Research Sources

   The computer industry has found it necessary to spend vast sums on
marketing its products and whilst some of that effort is devoted to
'image' and 'concept' type advertising--to making senior management
comfortable with the idea of the XXX Corporation's hardware because
it has 'heard' of it--much more is in the form of detailed product

   This information surfaces in glossies, in conference papers, and
in magazine journalism. Most professional computer magazines are
given away on subscription to 'qualified' readers; mostly the
publisher wants to know if the reader is in a position to influence a
key buying decision--or is looking for a job.

   I have never had any difficulty in being regarded as qualified:
certainly no one ever called round to my address to check up the size
of my mainframe installation or the number of employees. If in doubt,
you can always call yourself a consultant.  Registration is usually a
matter of filling in a post-paid card. My experience is that, once
you are on a few subscription lists, more magazines, unasked for,
tend to arrive every week or month--together with invitations to
expensive conferences in far-off climes. Do not be put off by the
notion that free magazines must be garbage. In the computer industry,
as in the medical world, this is absolutely not the case. Essential
regular reading for hackers are Computing, Computer Weekly, Software,
Datalink, Communicate, Communications Management, Datamation,
Mini-Micro Systems, and Telecommunications.

** Page 52

   The articles and news items often contain information of use to
hackers: who is installing what, where; what sort of facilities are
being offered; what new products are appearing and what features they
have.  Sometimes you will find surveys of sub-sets of the computer
industry. Leafing through the magazine pile that has accumulated
while this chapter was being written, I have marked for special
attention a feature on Basys Newsfury, an electronic newsroom package
used, among others, by ITN's Channel Four News; several articles on
new on-line hosts; an explanation of new enhanced Reuters services; a
comparison of various private viewdata software packages and who is
using them; some puffs for new Valued Added Networks (VANs); several
pieces on computer security; news of credit agencies selling
on-line and via viewdata; and a series on Defence Data Networks.

   In most magazines, however, this is not all: each advertisement is
coded with a number which you have to circle on a tear-out post-paid
'bingo card': each one you mark will bring wads of useful
information: be careful, however, to give just enough information
about yourself to ensure that postal packets arrive and not
sufficient to give the 'I was just passing in the neighbourhood and
thought I would call in to see if I could help' sales rep a 'lead' he
thinks he can exploit.

   Another excellent source of information are exhibitions: there are
the ubiquitous 'product information' sheets, but also the actual
machines and software to look at and maybe play with; perhaps you can
even get a full scale demonstration and interject a few questions.
The real bonus of exhibitions, of course, is that the security sense
of salespersons, exhausted by performing on a stand for several days
and by the almost compulsory off-hours entertainment of top clients
or attempted seduction of the hired-in 'glamour' is rather low.
Passwords are often written down on paper and consulted in your full
view. All you need is a quick eye and a reasonable memory.

   At both exhibitions and conferences it is a good idea to be a
freelance journalist.  Most computer mags have relatively small
full-time staff and rely on freelancers, so you won't be thought odd.
And you'll have your questions answered without anyone asking 'And
how soon do you think you'll be making a decision? Sometimes the lack
of security at exhibitions and demonstrations defies belief. When ICL
launched its joint venture product with Sinclair, the One-Per-Desk
communicating executive work- stations; it embarked on a modest
road-show to give hands-on experience to prospective purchasers. The
demonstration models had been pre-loaded with phone numbers...of
senior ICL directors, of the ICL mainframe at its headquarters in
Putney and various other remote services....

** Page 53

   Beyond these open sources of information are a few murkier ones.
The most important aid in tackling a 'difficult' operating system or
applications program is the proper documentation: this can be
obtained in a variety of ways. Sometimes a salesman may let you look
at a manual while you 'help' him find the bit of information he can't
remember from his sales training. Perhaps an employee can provide a
'spare', or run you a photocopy. In some cases, you may even find the
manual stored electronically on the system; in which case, print it
out. Another desirable document is an organisation's internal phone
book...it may give you the numbers for the computer ports, but
failing that, you will be able to see the range of numbers in use
and, if you are using an auto-dial modem coupled with a
search-and-try program, you will be able to define the search
parameters more carefully. A phone book will also reveal the names of
computer managers and system engineers; perhaps they use fairly
obvious passwords.

   It never ceases to astonish me what organisations leave in refuse
piles without first giving them a session with the paper shredder.

   I keep my cuttings carefully stored away in a second-hand filing
cabinet; items that apply to more than one interest area are
duplicated in the photocopier.


   But hackers' research doesn't rely simply on collecting vast
quantities of paper against a possible use. If you decide to target
on a particular computer or network, it is surprising what can be
found out with just a little effort.  Does the organisation that owns
the system publish any information about it.  In a handbook, annual
report, house magazine? When was the hardware and software installed?
Did any of the professional weekly computer mags write it up? What do
you know about the hardware, what sorts of operating systems would
you expect to see, who supplied the software, do you know anyone with
experience of similar systems, and so on.

   By way of illustration, I will describe certain inferences it is
reasonable to make about the principal installation used by Britain's
Security Service, MI5. At the end, you will draw two conclusions:
first that someone seriously interested in illicitly extracting
information from the computer would find the traditional techniques
of espionage--suborning of MI5 employees by bribery, blackmail or
appeal to ideology--infinitely easier than pure hacking; and second,
that remarkable detail can be accumulated about machines and
systems, the very existence of which is supposed to be a secret--and
by using purely open sources and reasonable guess-work.

** Page 54

   The MI5 databanks and associated networks have long been the
subject of interest to civil libertarians. Few people would deny
absolutely the need for an internal security service of some sort,
nor deny that service the benefit of the latest technology. But,
civil libertarians ask, who are the legitimate targets of MI5's
activities? If they are 'subversives', how do you define them? By
looking at the type of computer power MI5 and its associates possess,
it possible to see if perhaps they are casting too wide a net for
anyone's good. If, as has been suggested, the main installation can
hold and access 20 million records, each containing 150 words, and
Britain's total population including children, is 56 million, then
perhaps an awful lot of individuals are being marked as 'potential

   It was to test these ideas out that two journalists, not
themselves out-and-out hackers, researched the evidence upon which
hackers have later built. The two writers were Duncan Campbell of the
New Statesman and Steve Connor, first of Computing and more recently
on the New Scientist.  The inferences work this way: the only
computer manufacturer likely to be entrusted to supply so sensitive a
customer would be British and the single candidate would be ICL. You
must therefore look at their product range and decide which items
would be suitable for a really large, secure, real-time database
management job. In the late 1970s, the obvious path was the 2900
series, possibly doubled up and with substantive rapid-access disc
stores of the type EDS200.

   Checking through back issues of trade papers it is possible to see
that just such a configuration, in fact a dual 2980 with a 2960 as
back-up and 20 gigabytes of disc store, were ordered for classified
database work by the Ministry of Defence'. ICL, on questioning by
the journalists, confirmed that they had sold 3 such large systems
two abroad and one for a UK government department. Campbell and
Connor were able to establish the site of the computer, in Mount Row,
London W1, and, in later stories, gave more detail, this time
obtained by a careful study of advertisements placed by two
recruitment agencies over several years. The main computer, for
example, has several minis attached to it, and at least 200
terminals. The journalists later went on to investigate details of
the networks--connections between National Insurance, Department of
Health, police and vehicle driving license Systems.

   In fact, at a technical level, and still keeping to open sources,
You can build up even more detailed speculations about the MI5 main

** Page 55

ICL's communication protocols, CO1, C02, C03, are published items;
you can get terminal emulators to work on a PC, and both the company
and its employees have published accounts of their approaches to
database management systems, which, incidentally, integrate software
and hardware functions to an unusually high degree, giving speed but
also a great deal of security at fundamental operating system level.

   Researching MI5 is an extreme example of what is possible; there
are few computer installations of which it is in the least difficult
to assemble an almost complete picture.

** Page 56


Hackers' Techniques

   The time has now come to sit at the keyboard, phone and modems at
the ready, relevant research materials convenient to hand and see
what you can access. In keeping with the 'handbook' nature of this
publication, I have put my most solid advice in the form of a
trouble-shooting appendix (I), so this chapter talks around the
techniques rather than spelling them out in great detail.

   Hunting instincts Good hacking, like birdwatching and many other
pursuits, depends ultimately on raising your intellectual knowledge
almost to instinctive levels. The novice twitcher will, on being told
'There's a kingfisher!', roam all over the skies looking for the
little bird and probably miss it. The experienced ornithologist will
immediately look low over a patch of water, possibly a section shaded
by trees, because kingfishers are known to gulp the sort of flies
that hover over streams and ponds. Similarly, a good deal of skilful
hacking depends on knowing what to expect and how to react. The
instinct takes time to grow, but the first step is understanding that
you need to develop it in the first place.

Tricks with phones

   If you don't have a complete phone number for a target computer,
then you can get an auto-dialler and a little utility program to
locate it for you. You will find a flow-chart for a program in
Appendix VII. An examination of the phone numbers in the vicinity of
the target machine should give you a range within which to search.
The program then accesses the auto-dial mechanism of the modem and
'listens' for any whistles. The program should enable the phone line
to be disconnected after two or three 'rings' as auto-anSwer modems
have usually picked up by then.

   Such programs and their associated hardware are a little more
Complicated than the popularised portrayals suggest: you must have
software to run sequences of calls through your auto-dialler, the
hardware must tell you whether you have scored a 'hit' with a modem
or merely dialled a human being, and, since the whole point of the
exercise is that it works unattended, the process must generate a
list of numbers to try.

** Page 57

Logging on

   You dial up, hear a whistle...and the VDU stays blank. What's gone
wrong?  Assuming your equipment is not at fault, the answer must lie
either in wrong speed setting or wrong assumed protocol. Experienced
hackers listen to a whistle from an unknown computer before throwing
the data button on the modem or plunging the phone handset into the
rubber cups of an acoustic coupler.  Different tones indicate
different speeds and the trained ear can easily detect the
difference--appendix III gives the common variants.

   Some modems, particularly those on mainframes, can operate at more
than one speed; the user sets it by sending the appropriate number of
carriage returns. In a typical situation, the mainframe answers at
110 baud (for teletypewriters), and two carriage returns take it up
to 300 baud, the normal default for asynchronous working.

   Some hosts will not respond until they receive a character from
the user. Try sending a space or a carriage return.

   If these obvious things don't work and you continue to get no
response, try altering the protocol settings (see chapters 2 and 3).
Straightforward asynchronous protocols with 7-bit ASCII, odd or even
parity and surrounded by one stop and one start bit is the norm, but
almost any variant is possible.

   Once you start getting a stream from the host, you must evaluate
it to work out what to do next. Are all the lines over-writing each
other and not scrolling down the screen? Get your terminal software
to insert carriage returns. Are you getting a lot of corruption?
Check your phone connections and your protocols. The more familiar
you are with your terminal software at this point, the more rapidly
you will get results.


   Everyone thinks they know how to invent plausible and acceptable
passwords; here are the ones that seem to come up over and over


** Page 58

   Are you puzzled by the special inclusion of FRED? Look at your
computer keyboard sometime and see how easily the one-fingered typist
can find those four letters!

   If you know of individuals likely to have legitimate access to a
system, find out what you can about them to see if you can
second-guess their choice of personal password. Own names, or those
of loved ones, or initials are the top favourites. Sometimes there is
some slight anagramming and other forms of obvious jumbling. If the
password is numeric, the obvious things to try are birthdays, home
phone numbers, vehicle numbers, bank account numbers (as displayed on
cheques) and so on.

   Sometimes numeric passwords are even easier to guess: I have found
myself system manager of a private viewdata system simply by offering
it the password 1234567890 and other hackers have been astonished at
the results obtained from 11111111, 22222222 etc or 1010101, 2020202.

It is a good idea to see if you can work on the mentality and known
pre-occupations of the legitimate password holder: if he's keen on
classic rock'n'roll, you could try ELVIS; a gardener might choose
CLEMATIS; Tolkien readers almost invariably select FRODO or BILBO;
those who read Greek and Roman Literature at ancient universities
often assume that no one would ever guess a password like EURIPIDES;
it is a definitive rule that radio amateurs never use anything other
than their call-signs.

   Military users like words like FEARLESS and VALIANT or TOPDOG;
universities, large companies and public corporations whose various
departments are known by acronyms (like the BBC) can find those
initials reappearing as passwords.

   One less-publicised trick is to track down the name of the top
person in the organisation and guess a computer identity for them;
the hypothesis is that they were invited to try the computer when it
was first opened and were given an 'easy' password which has neither
been used since nor wiped from the user files. A related trick is to
identify passwords associated with the hardware or software
installer; usually the first job of a system manager on taking over a
computer is to remove such IDs, but often they neglect to do so.
Alternatively, a service engineer may have a permanent ID so that, if
the system falls over, it can be returned to full activity with the
minimum delay.

   Nowadays there is little difficulty in devising theoretically
secure password systems, and bolstering them by allowing each user
only three false attempts before the disconnecting the line, as
Prestel does, for example. The real difficulty lies in getting humans
to follow the appropriate procedures. Most of us can only hold a
limited quantity of character and number sequences reliably in our

** Page 59

Make a log-on sequence too complicated, and users will feel compelled
to write little notes to themselves, even if expressly forbidden to
do so.  After a while the complicated process becomes
counter-productive. I have a encrypting/decrypting software pack- age
for the IBM PC. It is undoubtedly many times more secure than the
famous Enigma codes of World War II and after.  The trouble is that
that you need up to 25 different 14-digit numbers of your
specification, which you and your correspondent must share if
successful recovery of the original text is to take place.

   Unfortunately the most convenient way to store these sequences is
in a separate disk file (get one character wrong and decryption is
impossible) and it is all too easy to save the key file either with
the enciphered stream, or with the software master, in both of which
locations they are vulnerable.

   Nowadays many ordinary users of remote computer services use
terminal emulator software to store their passwords. It is all too
easy for the hacker to make a quick copy of a 'proper' user's disk,
take it away, and then examine the contents of the various log-on
files--usually by going into an 'amend password' option. The way for
the legitimate user to obtain protection, other than the obvious one
of keeping such disks secure, is to have the terminal software itself
password protected, and all files encrypted until the correct
password is input. But then that new password has to be committed to
the owner's memory....

   Passwords can also be embedded in the firmware of a terminal.
This is the approach used in many Prestel viewdata sets when the user
can, sometimes with the help of the Prestel computer, program his or
her set into an EAROM (Electrically Alterable Read Only Memory). If,
in the case of Prestel, the entire 14-digit sequence is permanently
programmed in the set, that identity (and the user bill associated
with it) is vulnerable to the first person who hits the 'viewdata'
button on the keypad. Most users only program in the first 10 digits
and key in the last four manually. A skilful hacker can make a
terminal disgorge its programmed ID by sticking a modem in
answer-mode on its back (reversing tones and, in the case of
viewdata, speeds also) and sending the ASCII ENQ (ctrl-E) character,
which will often cause the user's terminal to send its identity.

   A more devious trick with a conventional terminal is to write a
little program which overlays the usual sign-on sequence. The program
captures the password as it is tapped out by the legitimate user and
saves it to a file where the hacker can retrieve it later.

** Page 60

   People reuse their passwords. The chances are that, if you obtain
someone's password on one system, the same one will appear on another
system to which that individual also has access.

Programming tricks

   In most longish magazine articles about electronic crime, the
writer includes a list of 'techniques' with names like Salami, Trap
Door and Trojan Horse.  Most of these are not applicable to pure
hacking, but refer to activities carried out by programmers
interested in fraud.

   The Salami technique, for example, consists of extracting tiny
sums of money from a large number of bank accounts and dumping the
proceeds into an account owned by the frauds man.  Typically there's
an algorithm which monitors deposits which have as their last digit
'8'; it then deducts '1' from that and then 1 or $1 is siphoned off.

   The Trojan Horse is a more generalised technique which consists of
hiding away a bit of unorthodox active code in a standard legitimate
routine.  The code could, for example, call a special larger routine
under certain conditions and that routine could carry out a rapid
fraud before wiping itself out and disappearing from the system for

   The Trap Door is perhaps the only one of these techniques that
pure hackers use. A typical case is when a hacker enters a system
with a legitimate identity but is able to access and alter the user
files.  The hacker than creates a new identity with extra privileges
to roam over the system, and is thus able to enter it at any time as
a 'super-user' or 'system manager'.

Hardware tricks

   For the hacker with some knowledge of computer hardware and
general electronics, and who is prepared to mess about with circuit
diagrams, a soldering iron and perhaps a voltmeter, logic probe or
oscilloscope, still further possibilities open up. One of the most
useful bits of kit consists of a small cheap radio receiver (MW/AM
band), a microphone and a tape recorder.  Radios in the vicinity of
computers, modems and telephone lines can readily pick up the chirp
chirp of digital communications without the need of carrying out a
physical phone 'tap'.

   Alternatively, an inductive loop with a small low-gain amplifier in
the vicinity of a telephone or line will give you a recording you can
analyse later at your leisure. 

** Page 61

By identifying the pairs of tones being used, you can separate the
caller and the host. By feeding the recorded tones onto an
oscilloscope display you can freeze bits, 'characters' and 'words';
you can strip off the start and stop bits and, with the aid of an
ASCII-to-binary table, examine what is happening. With experience it
is entirely possible to identify a wide range of protocols simply
from the 'look' of an oscilloscope.  A cruder technique is simply to
record and playback sign-on sequences; the limitation is that, even
if you manage to log on, you may not know what to do afterwards.

   Listening on phone lines is of course a technique also used by
some sophisticated robbers. In 1982 the Lloyds Bank Holborn branch
was raided; the alarm did not ring because the thieves had previously
recorded the 'all-clear' signal from the phone line and then, during
the break-in, stuffed the recording up the line to the alarm
monitoring apparatus.

   Sometimes the hacker must devise ad hoc bits of hardware trickery
in order to achieve his ends. Access has been obtained to a
well-known financial prices service largely by stringing together a
series of simple hardware skills. The service is available mostly on
leased lines, as the normal vagaries of dial-up would be too
unreliable for the City folk who are the principal customers.

   However, each terminal also has an associated dial-up facility, in
case the leased line should go down; and in addition, the same
terminals can have access to Prestel. Thus the hacker thought that it
should be possible to access the service with ordinary viewdata
equipment instead of the special units supplied along with the annual
subscription.  Obtaining the phone number was relatively easy: it was
simply a matter of selecting manual dial-up from the appropriate
menu, and listening to the pulses as they went through the regular

   The next step was to obtain a password. The owners of the terminal
to which the hacker had access did not know their ID; they had no
need to know it because it was programmed into the terminal and sent
automatically. The hacker could have put a micro 'back-to-front'
across the line and sent a ENQ to see if an ID would be sent back.
Instead he tried something less obvious.

   The terminal was known to be programmable, provided one knew how
and had the right type of keyboard.  Engineers belonging to the
service had been seen doing just that. How could the hacker acquire
'engineer' status? He produced the following hypothesis: the keyboard
used by the service's customers was a simple affair, lacking many of
the obvious keys used by normal terminals; the terminal itself was
manufactured by the same company that produced a range of editing
terminals for viewdata operators and publishers. Perhaps if one
obtained a manual for the editing terminal, important clues might
appear. A suitable photocopy was obtained and, lo and behold, there
were instructions for altering terminal IDs, setting auto-diallers
and so on.

** Page 62

   Now to obtain a suitable keyboard.  Perhaps a viewdata editing
keyboard or a general purpose ASCII keyboard with switchable baud
rates? So far, no hardware difficulties. An examination of the back
of the terminal revealed that the supplied keypads used rather
unusual connectors, not the 270 6-pin DIN which is the Prestel
standard. The hacker looked in another of his old files and
discovered some literature relating to viewdata terminals. Now he
knew what sort of things to expect from the strange socket at the
back of the special terminal: he pushed in an unterminated plug and
proceeded to test the free leads with a volt-meter against what he
expected; eight minutes and some cursing later he had it worked out;
five minutes after that he had built himself a little patch cord
between an ASCII keyboard, set initially to 75 baud and then to 1200
baud as the most likely speeds; one minute later he found the
terminal was responding as he had hoped...

   Now to see if there were similarities between the programming
commands in the equipment for which he had a manual and the equipment
he wished to hack. Indeed there were: on the screen before him was
the menu and ID and phone data he had hoped to see. The final test
was to move over to a conventional Prestel set, dial up the number
for the financial service and send the ID.

   The hacker himself was remarkably uninterested in the financial
world and, after describing to me how he worked his trick, has now
gone in search of other targets.

Operating Systems

   The majority of simple home micros operate only in two modes--
Basic or machine code. Nearly all computers of a size greater than
this use operating systems which are essentially housekeeping
routines and which tell the processor where to expect instructions
from, how to identify and manipulate both active and stored memory,
how to keep track of drives and serial ports (and Joy-sticks and
mice), how to accept data from a keyboard and locate it on a screen,
how to dump results to screen or printer or disc drive, and so on.
Familiar micro-based operating systems lnclude CP/M, MS-DOS, CP/M-86
and so on, but more advanced operating systems have more
facilities--capacity to allow several users all accessing the same
data and programs without colliding with each other, enlarged
standard utilities to make fast file creation, fast sorting and fast
calculation much easier. Under Simple operating systems, the
programmer has comparatively few tools to help him; often there is
just the Basic language, which elf contains no standard
procedures--almost everything must be written from scratch each time.

** Page 63

But most computer programs rely, in essence, on a small set of
standard modules: forms to accept data to a program, files to keep
the data in, calculations to transform that data, techniques to sort
the data, forms to present the data to the user upon demand, the
ability to present results in various graphics, and so on. So
programs written under more advanced operating systems tend to be
comparatively briefer for the same end-result than those with Basic
acting not only as a language, but also as the computer's

   When you enter a mainframe computer as an ordinary customer, you
will almost certainly be located in an applications program, perhaps
with the capacity to call up a limited range of other applications
programs, whilst staying in the one which has logged you on as user
and is watching your connect-time and central processor usage.

   One of the immediate aims of a serious hacker is to get out of
this environment and see what other facilities might be located on
the mainframe. For example, if access can be had to the user-log it
becomes possible for the hacker to create a whole new status for
himself, as a system manager, engineer, whatever. The new status,
together with a unique new password, can have all sorts o f
privileges not granted to ordinary users. The hacker, having acquired
the new status, logs out in his original identity and then logs back
with his new one.

   There is no single way to break out of an applications program
into the operating system environment; people who do so seldom manage
it by chance: they tend to have had some experience of a similar
mainframe. One of the corny ways is to issue a BREAK or ctrl-C
command and see what happens; but most applications programs
concerned with logging users on to systems tend to filter out
'disturbing' commands of that sort. Sometimes it easier to go beyond
the logging-in program into an another 'authorised' program and try
to crash out of that. The usual evidence for success is that the
nature of the prompts will change. Thus, on a well-known mini family
OS, the usual user prompt is

      COMMAND ?

or simply


** Page 64

Once you have crashed out the prompt may change to a simple




or even


it all depends.

   To establish where you are in the system, you should ask for a
directory; DIR or its obvious variants often give results. Directories
may be hierarchical, as in MS-DOS version 2 and above, so that at
the bottom level you simply get directories of other directories.
Unix machines are very likely to exhibit this trait. And once you get
a list of files and programs...well, that's where the exploration
really begins.

   In 1982, two Los Angeles hackers, still in their teens, devised
one of the most sensational hacks so far, running all over the
Pentagon's ARPA data exchange network. ARPAnet was and is the
definitive packet-switched network (more about these in the next
chapter). It has been running for twenty years, cost more than $500m
and links together over 300 computers across the United States and
beyond. Reputedly it has 5,000 legitimate customers, among them
NORAD, North American Air Defence Headquarters at Omaha, Nebraska.
Ron Austin and Kevin Poulsen were determined to explore it.

   Their weapons were an old TRS-80 and a VIC-20, nothing
complicated, and their first attempts relied on password-guessing.
The fourth try, 'UCB', the obvious initials of the University of
California at Berkeley, got them in. The password in fact was little
used by its legitimate owner and in the end, it was to be their

   Aspects of ARPAnet have been extensively written up in the
text-books simply because it has so many features which were first
tried there and have since become 'standard' on all data networks.
From the bookshop at UCLA, the hackers purchased the manual for UNIX,
the multi-tasking, multi-user operating system devised by Bell
Laboratories, the experimental arm of AT&T, the USA's biggest
telephone company.

** Page 65

At the heart of Unix is a small kernel containing system primitives;
Unix instructions are enclosed in a series of shells, and very
complicated procedures can be called in a small number of text lines
simply by defining a few pipes linking shells. Unix also contains a
large library of routines which are what you tend to find inside the
shells. Directories of files are arranged in a tree-like fashion,
with master or root directories leading to other directories, and so

   Ron and Kevin needed to become system 'super-users' with extra
privileges, if they were to explore the system properly; 'UCB' was
merely an ordinary user. Armed with their knowledge of Unix, they set
out to find the files containing legitimate users' passwords and
names. Associated with each password was a Unix shell which defined
the level of privilege. Ron wrote a routine which captured the
privilege shell associated with a known super-user at the point when
that user signed on and then dumped it into the shell associated with
a little-used identity they had decided to adopt for their own
explorations. They became 'Jim Miller'; the original super-user lost
his network status. Other IDs were added. Captured privilege shells
were hidden away in a small computer called Shasta at Stanford, at
the heart of California's Silicon Valley.

   Ron and Kevin were now super-users. They dropped into SRI,
Stanford Research Institute, one of the world's great centres of
scientific research; into the Rand Corporation, known equally for its
extensive futurological forecasting and its 'thinking about the
unthinkable', the processes of escalation to nuclear war; into the
National Research Laboratory in Washington; into two private research
firms back in California and two defence contractors on the East
Coast; and across the Atlantic to the Norwegian Telecommunications
Agency which, among other things, is widely believed to have a
special role in watching Soviet Baltic activity. And, of course,

   Their running about had not gone unnoticed; ARPAnet and its
constituent computers keep logs of activity as one form of security
(see the section below) and officials both at UCLA (where they were
puzzled to see an upsurge in activity by 'UCB') and in one of the
defence contractors sounded an alarm. The KGB were suspected, the FBI

   One person asked to act as sleuth was Brian Reid, a professor of
electrical engineering at Stanford. He and his associates set up a
series of system trips inside a Unix shell to notify them when
certain IDs entered an ARPAnet computer. His first results seemed to
indicate that the source of the hacking was Purdue, Indiana, but the
strange IDs seemed to enter ARPAnet from all over the place.

** Page 66

Eventually, his researches lead him to the Shasta computer and he had
identified 'Miller' as the identity he had to nail. He closed off
entry to Shasta from ARPanet.  'Miller' reappeared; apparently via a
gateway from another Stanford computer, Navajo. Reid, who in his
sleuthing role had extremely high privileges, sought to wipe 'Miller'
out of Navajo. A few minutes after 'Miller' had vanished from his
screen, he re- appeared from yet another local computer, Diablo. The
concentration of hacking effort in the Stanford area lead Reid to
suppose that the origin of the trouble was local. The most effective
way to catch the miscreant was by telephone trace. Accordingly, he
prepared some tantalising, apparently private, files. This was bait,
designed to keep 'Miller' online as long as possible while the FBI
organised a telephone trace. 'Miller' duly appeared, the FBI went
into action--and arrested an innocent businessman.

   But back at UCLA they were still puzzling about 'UCB'. In one of
his earliest sessions, Ron had answered a registration questionnaire
with his own address, and things began to fall into place. In one of
his last computer 'chats' before arrest, Kevin, then only 17 and only
beginning to think that he and his friend might have someone on their
trail, is supposed to have signed off: 'Got to go now, the FBI is
knocking at my door.' A few hours later, that is exactly what

Computer Security Methods

   Hackers have to be aware of the hazards of being caught: there is
now a new profession of computer security experts, and they have had
some successes.  The first thing such consultants do is to attempt to
divide responsibility within a computer establishment as much as
possible. Only operators are allowed physical access to the
installation, only programmers can use the operating system (and
under some of these, such as VM, maybe only part of it.). Only system
managers are permitted to validate passwords, and only the various
classes of users are given access to the appropriate applications

   Next, if the operating system permits (it usually does), all
accesses are logged; surveillance programs carry out an audit, which
gives a historic record, and also, sometimes, perform monitoring,
which is real-time surveillance.

   In addition, separate programs may be in existence the sole
purpose of which is threat monitoring: they test the system to see if
anyone is trying repeatedly to log on without apparent success (say
by using a program to try out various likely passwords).

** Page 67

   They assess if any one port or terminal is getting more than usual
usage, or if IDs other than a regular small list start using a
particular terminal--as when a hacker obtains a legitimate ID but one
that normally operates from only one terminal within close proximity
to the main installation, whereas the hacker is calling from outside.

   Increasingly, in newer mainframe installations, security is built
into the operating system at hardware level. In older models this was
not done, partly because the need was not perceived, but also because
each such 'unnecessary' hardware call tended to slow the whole
machine down. (If a computer must encrypt and decrypt every process
before it is executed, regular calculations and data accesses take
much longer.) However, the largest manufacturers now seem to have
found viable solutions for this problem....

** Page 68



   Until ten years ago, the telecommunications and computer
industries were almost entirely separate. Shortly they will be almost
completely fused. Most of today's hackers operate largely in
ignorance of what goes on in the lines and switching centres between
the computer they own and the computer they wish to access.
Increasingly, dedicated hackers are having to acquire knowledge and
experience of data networks, a task made more interesting, but not
easier, by the fact that the world's leading telecommunications
organisations are pushing through an unprecedented rate of
innovation, both technical and commercial.  Apart from purely local
lowspeed working, computer communications are now almost
exclusively found on separate high-speed data networks, separate that
is from the two traditional telecommunications systems telegraphy and
telephone. Telex lines operate typically at 50 or 75 baud with an
upper limit of 110 baud.

   The highest efficient speed for telephone-line-based data is 1200
baud. All of these are pitifully slow compared with the internal
speed of even the most sluggish computer. When system designers first
came to evaluate what sort of facilities and performance would be
needed for data communications, it became obvious that relatively few
lessons would be drawn from the solutions already worked out in voice

Analogue Networks

   In voicegrade networks, the challenge had been to squeeze as many
analogue signals down limited-size cables as possible. One of the
earlier solutions, still very widely used, is frequency division
multiplexing (FDM): each of the original speech paths is modulated
onto one of a specific series of radio frequency carrier waves; each
such rf wave is then suppressed at the transmitting source and
reinserted close to the receiving position so that only one of the
sidebands (the lower), the part that actually contains the
intelligence of the transmission, is actually sent over the main data
path.  This is similar to ssb transmission in radio.

The entire series of suppressed carrier waves are then modulated onto
a further carrier wave, which then becomes the main vehicle for
taking the bundle of channels from one end of a line to the other.

** Page 69

Typically, a small coaxial cable can handle 60 to 120 channels in
this way, but large cables (the type dropped on the beds of oceans
and employing several stages of modulation) can carry 2700 analogue
channels.  Changing audio channels (as they leave the telephone
instrument and enter the local exchange) into rf channels, as well as
making frequency division multiplexing possible, also brings benefits
in that over long circuits it is easier to amplify rf signals to
overcome losses in the cable.

   Just before World War II, the first theoretical work was carried
out to find further ways of economising on cable usage; what was then
developed is called Pulse Code Modulation (PCM).

   There are several stages. In the first, an analogue signal is
sampled at specific intervals to produce a series of pulses; this is
called Pulse Amplitude Modulation, and takes advantage of the
characteristic of the human ear that if such pulses are sent down a
line with only a very small interval between them, the brain smoothes
over the gaps and reconstitutes the entire original signal.

   In the second stage, the levels of amplitude are sampled and
translated into a binary code. The process of dividing an analogue
signal into digital form and then reassembling it in analogue form is
called quantization. Most PCM systems use 128 quantizing levels, each
pulse being coded into 7 binary digits, with an eighth added for
supervisory purposes.


   <------| SYN | CH1 | CH2 | CH3 | CH4 | SYN | CH1 |

   +-----------------+                        +-----------------+
 1 |                 |                        |                 |1
 --+                 |  +---+        +---+    |                 +--
 2 |                 |  |   |        |   |    |                 |2
 --+   MULTIPLEXER   |==+ M +--\/\/--+ M +==--+   MULTIPLEXER   +--
 3 |                 |  |   |        |   |    |                 |3
 --+                 |  +---+        +---+    |                 +--
 4 |                 |                        |                 |4
 --+-----------------+                        +-----------------+--

            | CH1 | SYN | CH4 | CH3 | CH2 | CH1 |SYN |------->

                         ONE DATA FRAME

** Page 70

   By interleaving coded characters in a highspeed digital stream it
is possible to send several separate voice channels along one
physical link. This process is called Time Division Multiplexing
(TDM) and together with FDM still forms the basis of most of the
globe's voicegrade communications.

Digital Networks

   Elegant though these solutions are, though, they are rapidly being
replaced by totally digital schemes. Analogue systems would be very
wasteful when all that is being transmitted are the discrete audio
tones of the output of a modem. In a speech circuit, the technology
has to be able to 'hear', receive, digitize and reassemble the entire
audio spectrum between 100 Hz and 3000 Hz, which is the usual
passband of what we have come to expect from the audio quality of the
telephone. Moreover, the technology must be sensitive to a wide range
of amplitude; speech is made up of pitch and associated loudness. In
a digital network, however, all one really wants to transmit are the
digits, and it doesn't matter whether they are signified by audio
tones, radio frequency values, voltage conditions or light pulses,
just so long as there is circuitry at either end which can encode and

   There are other problems with voice transmission: once two parties
have made a connection with each other (by the one dialling a number
and the other lifting a handset), good sense has suggested that it
was desirable to keep a total physical path open between them, it not
being practical to close down the path during silences and re-open it
when someone speaks. In any case the electromechanical nature of most
of today's phone exchanges would make such turning off and on very
cumbersome and noisy.

   But with a purely digital transmission, routing of a 'call'
doesn't have to be physical--individual blocks merely have to bear an
electronic label of their originating and destination addresses, such
addresses being 'read' in digital switching exchanges using chips,
rather than electromechanical ones. Two benefits are thus
simultaneously obtained: the valuable physical path (the cable or
satellite link) is only in use when some intelligence is actually
being transmitted and is not in use during 'silence'; secondly,
switching can be much faster and more reliable.

Packet Switching

   These ideas were synthesised into creating what has now become
packet switching. The methods were first described in the mid-1960's
but it was not until a decade later that suitable cheap technology
existed to create a viable commercial service.

** Page 71

The British Telecom product is called Packet SwitchStream (PSS) and
notable comparable US services are Compuserve, Telenet and Tymnet.
Many other countries have their own services and international packet
switching is entirely possible--the UK service is called,
unsurprisingly, IPSS.

International Packet Switched Services and DNICs


Datacalls can be made to hosts on any listed International Networks.
The NIC (Data Network Identification Code) must precede the
international host's NUA.  Charges quoted are for duration (per hour)
and volume (per Ksegment) and are raised in steps of 1 minute and 10
segments respectively.

Country             Network      DNIC

Australia           Midas         5053
8elgium             Euronet       2062
Belgium             Euronet       2063
Canada              Datapac       3020
Canada              Globedat      3025
Canada              Infoswitch    3029
Denmark             Euronet       2383
France              Transpac      2080
French Antilles     Euronet       3400
Germany (FDR)       Datex P       2624
Germany (FDR)       Euronet       2623
Hong Kong           IDAS          4542
Irish Republic      Euronet       2723
Italy               Euronet       2223
Japan               DDX-P         4401
Japan               Venus-P       4408
Luxembourg          Euronet       2703

** Page 72

Netherlands         Euronet       2043
Country             Network       DNIC
Norway              Norpak        2422
Portugal            N/A           2682
Singapore           Telepac       5252
South Africa        Saponet       6550
Spain               TIDA          2141
Sweden              Telepak       2405
Switzerland         Datalink      2289
Switzerland         Euronet       2283
U.S.A.              Autonet       3126
U.S.A.              Compuserve    3132
U.S.A.              ITT (UDTS)    3103
U.S.A.              RCA (LSDS)    3113
U.S.A.              Telenet       3110
U.S.A.              Tymnet        3106
U.S.A.              Uninet        3125
U.S.A.              WUI (DBS)     3104

Additionally, Datacalls to the U.K. may be initiated from:

Bahrain, Barbados, Bermuda, Israel, New Zealand and the United Arabs

Up to date Information can be obtained from IPSS Marketing on

   In essence, the service operates at 48kbits/sec full duplex (both
directions simultaneously) and uses an extension of time division
multiplexing Transmission streams are separated in convenient- sized
blocks or packets, each one of which contains a head and tail
signifying origination and destination. The packets are assembled
either by the originating computer or by a special facility supplied
by the packet switch system. The packets in a single transmission
stream may all follow the same physical path or may use alternate
routes depending on congestion. The packets from one 'conversation'
are very likely to be interleaved with packets from many Other
'conversations'. The originating and receiving computers see none of
this. At the receiving end, the various packets are stripped of their
routing information, and re-assembled in the correct order before
presentation to the computer's VDU or applications program.

** Page 73


                                           |            PSS
            o> o> o> o> o> o> o> o> o> o>    |     | O> O> O>
Terminal D================================-+ PAD +-==========
            <o ><o ><o ><o ><o ><o ><o ><o ><o ><o  |     || ><o ><o ><o
<o                ><o all public data networksusing packet switching seek to be
compatible with each other at least a considerable degree. the international
standard they have implement is called ccitt x.25. this multi-layered protocol covering (potentially) everything from electrical connections user interface. levels work like this:

7 application interface

6 presentation formatting & code conversion

5 session co-ordination between processes

4 transport control of quality service

3 network set up and maintenance

2 link reliable transfer

                       terminalphysical bitstream

** page 74 moment agreement has only been reached on lowest three network. above that there battle in progressibm
which solutions
problems under name sna (systems architecture)
most remainder
principal main- frame manufacturerswhose
solution osi (open systems interconnection).
single so much for background explanation. how does affect
user? users can accessone two ways. use special
terminals able create packets an appropriate form--called

(in original book diagram showing
dial-up termials connecting
pad system directly
connected pss. note added by electronic images) 75
jargon--and these sit
switch circuitaccessing it via nearest pss
exchange permanent dataline modems operating speeds 240048009600or 48k bauddepending
level traffic. alternatively customer ordinary asynchronous without packet-creating capabilities
connect into facility handles assembly him.such devices are assembler/ disassemblers
pads. jargon said character terminals. pads accessed either leased line 300      1200 thosebut also     110 1200/75. readers if used will done their own computers

   as dialling pad. phone numbers uk found directory
published telecom national networks. order you individual need identity (nui) registeredyour local (pse).
pse throw off dont give recognisable nui. extremely flexible configure ports suit equipmentboth speed screen addressingrather bulletin board (though
accurate mimics pad). speed:              (std)  1200/75 duplex

aberdeen         (0224)    642242      642484       642644
birmingham       (021)     2145139     2146191      241 3061
bristol          (0272)    216411      216511       216611cambridge        (0223)    82511       82411        82111
edinburgh        (031)     337 9141 9121 9393
glasgow          (041)     204 2011 2031 2051
leeds            (0532)    470711      470611       470811
liverpool        (051)     211 0000    212 5127     213 6327
london            (01)      825 9421    407 8344     928 2333 9111 3399 1737
luton            (0582)    8181        8191         8101
manchester       (061)     833 0242 0091 0631
newcastle/tyne   (0632)    314171      314181       314161
nottingham       (0602)    881311      881411       881511
portsmouth       (0705)    53011       53911        53811
reading          (0734)    389111      380111       384111
(*)slough        (0753)    6141        6131         6171

(*)local area slough not available. modem/dataphone receipt tone. 76

   next address (nua) host
calling. available same directory:
university computing servicess nua 234 222339399blaise
219200222istel 252724241 on. first four known dnic (data identification code) country ( identifier)
last specificsignifying get prestelthough purposes academic exercise: a9 1100 2018 gives
graphics (a9 indicates teletype

   once routed
computer choicethen exactly were entering direct dial password requested.  costs governed number
exchanged than distance actual time call. typical
thus contain following running costs: call (on
regular billtime-related) charges (dependent sent) bills (which could time-related per record fixed subscription). techniques confined uses them
its mini-network
various retrieval (the ones into)
update mailbox handle gateway connections. newer private switched. 77

   valued (vans) basic telecoms facilities some additional service--data processing
hosting publishing ventures example--has added. offering easier cheaper boon hacker. no longer hacker worry about protocols normally expects see
users. x.25 adaptability mean even comms talk
anything tariff structurefavouringmeans any anywhere
world target.

   austin poulsen arpanet hackersmade dramatic packet-switched net milwaukee 414s ran around gte
telenet biggest us.
self-adopted comes telephone
city chiefly hitherto centre american beer
industry.during spring summer 1983 publicly directories usual guessing games
pass-numbers pass-words dropped  security
pacific bank
los angeles sloan-kettering cancer clinic newyork (it still clear me actually altered patients
records merely looked them) canadian cement company alamos research laboratory mexicohome atomic
bomb where
nuclear weapons continues day.
believed saw sensitive classifiedfiles.

   commenting activities prominent
consultantjoesph coatessaid: babies great
kind kids anyone would - be...there nothing
wrong kids. problem idiots who sold ignorant people bought it. nobody should buy knowing . built in....you timid dealing foolish. couple months 1984british carried
out thorough exploration sercnet sponsored science engineering council
centred rutherford appleton cambridge. linkstogether technology universities polytechnics united kingdom gateways cern (european research). 78

almost every type mainframelarge mini-computer discovered hanging 3032 370
itselfprime 400s550s 750s over placevax 11/780s
oxforddaresbury vaxs durhameast anglia newcastle gec 4000 family members odd
pdp11 unix.

   penetration was achieved when appeared popular hobbyist suggestion instruction 40might results. soon typed demo asked establishmentthings started happen. several days left
lack eventually became obvious supposed suggests limited demonstration
casual had insecurely up. i remember night pulled down manual filewatching after scroll my vdu baud. do word
guide fetching lists addresses
mnemonics members. included extensive
descriptions relationpss-style complete chapter know certain forms shut appears
continue. best stories definite
ending. offer brief extracts captured sessions.

03eoehaae node 3. service?
fad>CALL 40
Welcome to SERCNET-PSS Gateway. Type HELP for help.

Gatew::~cInkging in
user HELP
ID last used Wednesday, 18 January 1984 16:53
Started - Wed 18 Jan 19a4 17:07:55
Please enter your name and establishment DEMO
Due to a local FTP problem messages entered via the HELP system
during the last month have been lost. Please resubmit if
problem/question is still outstanding 9/1/84

No authorisation is required for calls which do not incur charges at
the Gateway. There is now special support for TELEX. A TELEX service
may be announced shortlY.

Copies of the PSS Guide issue 4 are available on request to Program
Advisory Office at RAL, telephone 0235 44 6111 (direct dial in) or
0235 21900 Ext 6111. Requests for copies should no longer be placed
in this help system.

The following options are available:

** Page 79

Which option do you require? GUIDE
The program 'VIEW' is used to display the Gateway guide
Commands available are:
<cr> or N next page
p         previous page
n         list page n
+n or -n  go forward or back n pages
S         first page
E         last page
L/string  find line Containing string
F/string  find line beginning string
Q         exit from VIEW

VIEW Vn 6> Q
The following options are available:

Which option do you require? HELP
NOTES replies to user queries & other notes
GUIDE Is the complete Gateway user guide (including the Appendices)
TITLES 1- a list of SERCNET L PSS addresses & mnemonics (Guide
Appendix 1)
ERRORS List of error codes you may receive EXAMPLES are ome examples
of use of the Gateway (Guide Appendix 2)
QUIT exits from this session

The following options are available:

Which option do you require? TITLES

VIEW Vn o>

If you have any comments, please type them now, terminate with E
on a line on its own. Otherwise just type <cr>

CPU used: 2 ieu, Elapsed: 14 mins, IO: 2380 units, Break: 114
Budgets: this period = 32.000 AUs, used = 0.015 AU, left - 29.161 AUs
User HELP   terminal   2 logged out Wed 18 Jan 1984 17:21:59

84/04/18. 18.47.00.


>           ThE SERCNET - PSS Gateway

>                User's Guide

                                                A S Dunn

>Issue 4                                 16 February 1983


** Page 80

Frm 1; Next>
The SERCNET-PSS Gateway provides access from SERCNET to PSS and PSS
to SERCNET. It functions as a 'straight through' connection between
the networks, ie it is protocol transparant. It operates as a
Transport Level gateway, in accordance with the 'Yellow book'
Transport Service. However the present implementation does not have a
full Transport Service. and therefore there are some limitations in
the service provided. For X29 which is incompatible with the Yellow
book Transport Service. special facilities are provided for the input
of user identification and addresses.

No protocol conversion facilities are provided by the Gateway -
protocol conversion facilities (eg X29 - TS29) can be provided by
calling through a third party machine (usually on SERCNET).

The Transport Service addressing has been extended to include
authorisation fields, so that users can be billed for any charges
they incur.

The Gateway also provides facilities for users to inspect their
accounts and change their passwords, and also a limited HELP

User Interface

The interface which the user sees will depend on the local equipment
Frm 2; Next>

which he is attached. This may be a PAD in which case he will
probably be using the X29 protocol, or a HOST (DTE) in which case he
might be using FTP for example. The local equipment must have some
way of generating a Transport Service Called Address for the Gateway,
which also includes an authorisation field - the format of this is
described below. The documentation for the local system must
therefore be consulted in order to find out how to generate the
Transport Service Called Address. Some examples given in Appendix 2.

A facility is provided for the benefit of users without access to the
'Fast Select' facility, eg BT PAD users (but available to all X29
terminal users) whereby either a minimal address can be included in
the Call User Data Field or an X25 subaddress can be used and the
Call User Data Field left absent.

The authorisation and address can then be entered when prompted by
the Gateway.

Unauthorised Use
Frm 5: Next>

No unauthorised use of the Gateway is allowed regardless of whether
charges are Incurred at the Gateway or not.

However, there is an account DEMO (password will be supplied on
request) With a small allocation which is available for users to try
out the Gateway but it should be noted that excessive use of this
account will soon exhaust the allocation thus depriving others of its

Prospective users of the Gateway should first contact User Interface
Group In the Computing Division of the Rutherford Appleton


To connect a call through the Gateway the following information is
required in the Transport Service Called Address:

1) The name of the called network
2) Authorisation. consisting of a USERID, PASSWORD and ACCOUNT, and
optionally, a reverse charging request
3) The address of the target host on the called network

The format is as follows:

<netname>(<authorisation>).<host address>

1) <netname> is one of the following:

** Page 81

SERCNET   to connect to the SERC network
PSS       to connect to PSS
S         an alias for SERCNET
69        another alias for SERCNET

2)        <authorisation> is a list of positional or keyword
parameters or booleans as follows:

keyword   Meaning

US        User identifier
PW        User's password
AC        the account - not used at present - talen to be same as US
RF        'reply paid' request (see below)
R         reverse charging indicator (boolean)

keywords are separated from their values by '='.
keyword-value pairs positional parameters and booleans are separated
from each other by ','. The whole string is enclosed in parentheses:



All the above have exactly the same meaning. The first form is the
most usual.

When using positionals, the order is: US,PW,AC,RP,R

3)<host address> is the address of the machine being called on the
target network. It may be a compound address, giving the service
within the target machine to be used. It may begin with a mnemonic
instead of a full DTE address. A list of current mnemonics for both
SERCNET and PSS is given in Appendix 1.

A restriction of using the Gateway is that where a Transport Service
address (service name) is required by the target machine to identify
the service to be used, then this must be included explicitly by the
user in the Transport Service Called Address, and not assumed from
the mnemonic, since the Gateway cannot Inow from the mnemonic. which
protocol is being used.



Both the above would refer to the FTP service on the GEC 'B' machine
at Rutherford.

RLGB alone would in fact connect to the X29 server, since no service
name is Frm 7; Next>
required for X29.

In order to enable subaddresses to be entered more easily with PSS
addresses, the delimiter '-' can be used to delimit a mnemonic. When
the mnemonic is translated to an address the delimiting '-' is
deleted so that the following string is combined with the address.

SERC-99 is translated to 23422351919199

Putting the abovementioned three components together, a full
Transport Service Called Address might look like:


** Page 82

Of course a request for reverse charging on SERCNET is meaningless,
but not illegal.

Reply Paid Facility      (Omit at first reading)

In many circumstances it is necessary for temporary authorisation to
be passed to a third party. For example, the recipient of network
MAIL may not himself be authorised to use the Gateway, and therefore
the sender may wish to grant him temporary authorisation in order to
reply. With the Job Transfer and maniplulation protocol, there is a
requirement to return output documents from jobs which have been
executed on a remote site.

The reply paid facility is involved by including the RP keyword in the
authorisation. It can be used either as a boolean or as a
keyword-value pair. When used as a boolean, a default value of I is

The value of the RP parameter indicates the number of reply paid
calls which are to be authorised. All calls which use the reply paid
authorisation will be charged to the account of the user who
initiated the reply paid authorisation.

Frm 9; Next:

The reply paid authorisation parameters are transmitted to the
destination address of a call as a temporary user name and password
in the Transport Service Calling Address. The temporary user name and
password are in a form available for use by automatic systems in
setting up a reply to the address which initiated the original call.

Each time a successful call is completed using the temporary user
name and password, the number of reply paid authorisations is reduced
by 1, until there are none left, when no further replies are allowed.
In addition there is an expiry date of I week, after which the
authorisations are cancelled.

In the event of call failures and error situations, it is important
that the effects are clearly defined. In the following definitions,
the term 'fail' is used to refer to any call which terminates with
either a non-zero clearing cause or diagnostic code or both,
regardless of whether data has been communicated or not. The rules
are defined as follows:

1) If a call which has requested reply paid authorisation fails for
any reason, then the reply paid authorisation is not set up.

2) If the Gateway is unable to set up the reply paid authorisation
for any reason (eg insufficient space), then the call requesting the
authorisation will be refused.

3) A call which is using reply paid authorisation may not create
another reply paid authorisation.

4) If a call which is using reply paid authorisation fails due to a
network error (clearing cause non zero) then the reply paid count is
not reduced.

5) If a call which is using reply paid authorisation fails due to a
host clearing (clearing cause zero, diagnostic code non-zero) then
the reply paid count is reduced, except where the total number of
segments transferred on the call is zero (ie call setup was never

Frm 11; Next?

X29 Terminal Protocol

There is a problem in that X29 is incompatible with the Transport
Service.  For this reason, it is possible that some PAD
implementations will be unable to generate the Transport Service
Called Address. Also some PAD's, eg the British Telecom PAD, may be
unable to generate Fast Select calls - this means that the Call User
Data Field is only 12 bytes long - insufficient to hold the Transport
Service Address.

If a PAD is able to insert a text string into the Call User Data Field
beginning at the fifth byte, but is restricted to 12 characters
because of inability to generate Fast Select calls, then a partial
address can be included consisting of either the network name being
called, or the network name plus authorisation.

** Page 83

The first character is treated as a delimiter, and should be entered
as the character '7'. This is followed by the name of the called
network - SERCNET.

Alternatively, if the PAD is incapable of generating a Call User Data
Field, then the network name can be entered as an X25 subaddress. The
mechanism employed by the Gateway is to transcribe the X25 subaddress
to the beginning of the Transport Service Called Address, converting
the digits of the subaddress into ASCII characters in the process.
Note that this means only SERCNET can be called with this method at
present by using subaddress 69.

The response from the Gateway will be the following message:

Please enter your authorisation and address required in form:

Reply with the appropriate response eg:


There is a timeout of between 3 and 4 minutes for this response.
after which the call will be cleared. There is no limit to the number
of attempts which may be made within this time limit - if the
authorisation or address entered is invalid, the Gateway will request
it again. To abandon the attempt. the call should be cleared from the
local PAD.

A restriction of this method of use of the Gateway is that a call
must be correctly authorised by the Gateway before charging can
begin, thus reverse charge calls from PSS which do not contain
authorisation in the Call Request packet will be refused. However it
is possible to include the authorisation but not the address in the
Call Request packet. The authorisation must then be entered again
together with the address when requested by the Gateway.

The above also applies when using a subaddress to identify the called
network. In this case the Call User Data Field will contain only the
authorisation in parentheses (preceded by the delimiter '@')

                                   - 5 -

Due to the lack of a Transport Service ACCEPT primitive in X29 it will be
found, on some PADs, that a 'call connected' message will appear on the
terminal as soon as the call has been connected to the Gateway. The 'call
connected' message should not be taken to imply that contact has been made
With the ultimate destination. The Gateway will output a message 'Call
connected to remote address' when the connection has been established.

Frm 14; Next

ITP Terminal Protocol

The terminal protocol ITP is used extensively on SERCNET and some
hosts support only this terminal protocol. Thus it will not be
possible to make calls directly between these hosts on SERCNET and
addresses on PSS which support only X29 or TS29. In these cases it
will be necessary to go through an intermediate machine on SERCNET
which supports both x29 and ITP or TS29 and ITP, such as a GEC ITP.
This is done by first making a call to the GEC MUM, and then making
an outgoing call from there to the desired destination.

PTS29 Terminal Protocol

This is the ideal protocol to use through the Gateway. since there
should be no problem about entering the Transport Service address.
However, it is divisable first to ascertain that the machine to be
called will support

When using this protocol, the service name of the TS29 server should be
entered explicitly, eg:

** Page 84



Due to the present lack of a full Transport Service in the Gateway,
some primitives are not fully supported.

In particular, the ADRESS, DISCONNECT and RESET primitives are not
fully supported. Howerver this should not present serious problems,
since the ADDRESS and REASET primitives are not widely used, and the
DISCONNECT primitive can be carried in a Clear Request packet.

Access to IPSS is through PSS. Just enter the IPSS address in place
of the PSS address.

................    and on and on for 17 pages

** Page 85


Viewdata Systems

   Viewdata, or videotex, has had a curious history. At one stage, in
the late 1970s, it was possible to believe that it was about to take
over the world, giving computer power to the masses via their
domestic tv sets. It was revolutionary in the time it was developed,
around 1975, in research laboratories owned by what was then called
the Post Office, but which is now British Telecom. It had a
colour-and-graphics display, a user-friendly means of talking to it
at a time when most computers needed precise grunts to make them
work, and the ordinary layperson could learn how to use it in five

   The viewdata revolution never happened, because Prestel, its most
public incarnation, was mismarketed by its owners, British Telecom,
and because, in its original version, it is simply too clumsy and
limited to handle more sophisticated applications. All information is
held on electronic file cards which can easily be either too big or
too small for a particular answer and the only way you can obtain the
desired information is by keying numbers, trundling down endless
indices. In the early days of Prestel, most of what you got was
indices, not substantive information. By the time that viewdata sets
were supposed to exist in their hundreds of thousands, home
computers, which had not been predicted at all when viewdata first
appeared, had already sold into the millionth British home.

   Yet private viewdata, mini-computers configured to look like
Prestel and to use the same special terminals, has been a modest
success. At the time of writing there are between 120 and 150
significant installations. They have been set up partly to serve the
needs of individual companies, but also to help particular trades,
industries and professions. The falling cost of viewdata terminals
has made private systems attractive to the travel trade, to retail
stores, the motor trade, to some local authorities and to the
financial world.

** Page 86

   The hacker, armed with a dumb viewdata set, or with a software
fix for his micro, can go ahead and explore these services. At the
beginning of this book, I said my first hack was of a viewdata
service. Viditel, the Dutch system. It is astonishing how many
British hackers have had a similar experience. Indeed, the habit of
viewdata hacking has spread throughout Europe also: the wonder- fully
named Chaos Computer Club of Hamburg had some well-publicised fun
with Bildschirmtext, the West German Prestel equivalent
colloquially-named Btx.

   What they appear to have done was to acquire the password of the
Hamburger Sparkasse, the country's biggest savings bank group.
Whereas telebanking is a relatively modest part of Prestel --the
service is called Homelink--the West German banks have been a
powerful presence on Btx since its earliest days. In fact, another
Hamburg bank, the Verbraucher Bank, was responsible for the world's
first viewdata Gateway, for once in this technology, showing the
British the way. The 25-member Computer Chaos Club probably acquired
the password as a result of the carelessness of a bank employee.
Having done so, they set about accessing the bank's own, rather high
priced, pages, some of which cost almost DM10 (2.70). In a
deliberate demonstration, the Club then set a computer to
systematically call the pages over and over again, achieving a
re-access rate of one page every 20 seconds. During a weekend in
mid-November 1984, they made more than 13,000 accesses and ran up a
notional bill of DM135,000 (36,000). Information Providers, of
course, are not charged for looking at their own pages, so no bill
was payable and the real cost of the hack was embarrassment.

   In hacking terms, the Hamburg hack was relatively trivial-- simple
password acquisition. Much more sophisticated hacks have been
perpertrated by British enthusiasts.

Viewdata hacking has three aspects: to break into systems and become
user, editor or system manager thereof; to discover hidden parts of
systems to which you have been legitimately admitted, and to uncover
new services.

Viewdata software structures

   An understanding of how a viewdata database is set up is a great
aid in learning to discover what might be hidden away.  Remember,
there are always two ways to each page--by following the internal
indexes, or by direct keying using *nnn#. In typical viewdata
software, each electronic file card or 'page' exists on an overall
tree-like structure:

** Page 87

      ---------------------+----------------------- ...
      1     2     3     4     5     6     7     8
      ------------+-------------------------------- ...
      31    32    33    34    35    36    37    38
      ------------------------+-------------------- ...
      351   352   353   354   355   356   357   358  3-digit
                   |                                 node
      -------------+------------------------------- ...
      3531  3532  3533  3534  3535  3536  3537  3538
      -------------------------------------------+-- ...

   Top pages are called parents; lower pages filials. Thus page 3538
needs parent pages 353, 35, 3 and 0 to support it, i.e. these pages
must exist on the system. On Prestel, the parents owned by
Information Providers (the electronic publishers) are 3 digits long
(3-digit nodes). Single and double-digit pages (0 to 99) are owned by
the 'system manager' (and so are any pages beginning with the
sequences 100nn-199nn and any beginning with a 9nnn). When a page is
set up by an Information Provider (the process of going into 'edit'
mode varies from software package to package; on Prestel, you call up
page 910) two processes are necessary--the overt page (i.e. the
display the user sees) must be written using a screen editor. Then
the IP must select a series of options--e.g. whether the page is for
gathering a response from the user or is just to furnish information;
whether the page is to be open for viewing by all, by a Closed User
Group, or just by the IP (this facility is used while a large
database is being written and so that users don't access part of it
by mistake); the price (if any) the page will bear--and the 'routing
instructions'. When you look at a viewdata page and it says 'Key 8
for more information on ABC', it is the routing table that is
constructed during edit that tells the viewdata computer: 'If a user
on this page keys 8, take him through to the following next page'.
Thus, page 353880 may say 'More information on ABC....KEY 8'. The
information on ABC is actually held on page 3537891. The routing
table on page 353880 will say: 8=3537891. In this example, you will
see that 3537891 i9 not a true filial of 353880--this does not
matter; however, in order for 3537891 to exist on the system, its
parents must exist, i.e.  there must be pages 353789, 35378, 3537

** Page 88

Input Details -

Update option o

Pageno 4190100         Frame-Id       a

User CUG               User access    y

Frame type i         Frame price 2p

          Choice type s

0-    *                  1-       4196121
2-    4196118            3-       4196120
4-    4196112            5-       4196119
6-    4196110            7-       *
8-    4190101            9-       4199

Prestel Editing. This is the 'choices' page which se s up the frame
before the overt page - the one the user sees - is prepared.

   These quirky features of viewdata software can help the hacker
search out hidden databases:

 * Using a published directory, you can draw up a list of 'nodes' and
who occupies them. You can then list out apparently 'unoccupied'
nodes and see if they contain anything interesting. It was when a
hacker spotted that an 'obvious' Prestel node, 456, had been unused
for a while, that news first got out early in 1984 about the Prestel
Micro computing service, several weeks ahead of the official

 * If you look at the front page of a service, you can follow the
routings of the main index--are all the obvious immediate filials
used? If not, can you get at them by direct keying?

** Page 89

 * Do any services start lower down a tree than you might expect
(i.e. more digits in a page number than you might have thought)? In
that case, try accessing the parents and see what happens.

 * Remember that you can get a message 'no such page' for two
reasons: because the page really doesn't exist, or because the
Information Provider has put it on 'no user access'. In the latter
case, check to see whether this has been done consistently--look at
the immediate possible filials.  To go back to when Prestel launched
its Prestel Microcom- puting service, using page 456 as a main node,
456 itself was closed off until the formal opening, but page 45600
was open.

Prestel Special Features

   In general, this book has avoided giving specific hints about
individual services, but Prestel is so widely available in the UK and
so extensive in its coverage that a few generalised notes seem

   Not all Prestel's databases may be found via the main index or in
the printed directories; even some that are on open access are
unadvertised. Of particular interest over the last few years have
been nodes 640 (owned by the Research and Development team at
Martlesham), 651 (Scratchpad--used for ad hoc demonstration
databases), 601 (mostly mailbox facilities but also known to carry
experimental advanced features so that they can be tried out), and
650 (News for Information Providers--mostly but not exclusively in a
Closed User Group). Occasionally equipment manufacturers offer
experimental services as well: I have found high-res graphics and
even instruction codes for digitised full video lurking around.

   In theory, what you find on one Prestel computer you will find on
all the others. In practice this has never been true, as it has
always been possible to edit individually on each computer, as well
as on the main updating machine which is supposed to broadcast to all
the others. The differences in what is held in each machine will
become greater over time.

   Gateway is a means of linking non-viewdata external computers to
the Prestel system. It enables on-screen buying and booking, complete
with validation and confirmation. It even permits telebanking, Most
'live' forms of gateway are very secure, with several layers of
password and security. However, gateways require testing before they
can be offered to the public; in the past, hackers have been able to
secure free rides out of Prestel....

** Page 90

   Careful second-guessing of the routings on the databases including
telesoftware(*) have given users free programs while the
telesoftware(*) was still being tested and before actual public

   Prestel, as far as the ordinary user is concerned, is a very
secure system--it uses 14-digit passwords and disconnects after three
unsuccessful tries. For most purposes, the only way of hacking into
Prestel is to acquire a legitimate user's password, perhaps because
they have copied it down and left it prominently displayed. Most
commercial viewdata sets allow the owner to store the first ten
digits in the set (some even permit the full 14), thus making the
casual hacker's task easier.  However, Prestel was sensationally
hacked at the end of October 1984, the whole system Iying at the feet
of a team of four West London hackers for just long enough to
demonstrate the extent of their skill to the press. Their success was
the result of persistence and good luck on their side and poor
security and bad luck on the part of BT. As always happens with
hacking activities that do not end up in court, some of the details
are disputed; there are also grounds for believing that news of the
hack was deliberately held back until remedial action had taken
place, but this is the version I believe:

   The public Prestel service consists of a network of computers,
mostly for access by ordinary users, but with two special-purpose
machines, Duke for IPs to update their information into and Pandora,
to handle Mailboxes (Prestel's variant on electronic mail). The
computers are linked by non-public packet-switched lines. Ordinary
Prestel users are registered (usually) onto two or three computers
local to them which they can access with the simple three-digit
telephone number 618 or 918. In most parts of the UK, these two
numbers will return a Prestel whistle. (BT Prestel have installed a
large number of local telephone nodes and

(*)Tefesoftware is a technique for making regular computer programs
available via viewdata the program lines are compressed according to
a simple set of rules and set up on a senes of viewdata frames. Each
frame contains a modest error-checking code. To receive a program,
the user's computer, under the control of a 'download' routine calls
the first program page down from the viewdata host, runs the error
check on it, and demands a re transmission if the check gives a
'false' If it gives a 'true', the user's machine unsqueezes the
programmes and dumps them into the Computers main memory or disc
store. It then requests the next viewdata page unfil the whole
program is collected. You then have a text file which must be
Converted into program instructions. Depending on what model of
micro you have, and which telesoftware package, you can either run
the program immediately or expect it. Personally I found the
telesoftware experience interesting the first time I tried it, and
quite useless in terms of speed, reliability and quality afterwards.

** Page 91

leased lines to transport users to their nearest machine at local
call rates, even though in some cases that machine may be 200 miles
away). Every Prestel machine also has several regular phone numbers
associated with it, for IPs and engineers. Most of these numbers
confer no extra privileges on callers: if you are registered to a
particular computer and get in via a 'back-door' phone number you
will pay Prestel and IPs exactly the same as if you had dialled 618
or 918. If you are not registered, you will be thrown off after three

   In addition to the public Prestel computers there are a number of
other BT machines, not on the network, which look like Prestel and
indeed carry versions of the Prestel database. These machines, left
over from an earlier stage of Prestel's development, are now used for
testing and development of new Prestel features. The old Hogarth
computer, originally used for international access, is now called
'Gateway Test' and, as its name implies, is used by IPs to try out
the interconnections of their computers with those of Prestel prior
to public release. It is not clear how the hackers first became aware
of the existence of these 'extra' machines; one version is that it
was through the acquisition of a private phone book belonging to a BT
engineer. Another version suggests that they tried 'obvious' log-in
pass-numbers--2222222222 1234--on a public Prestel computer and found
themselves inside a BT internal Closed User Group which contained
lists of phone numbers for the develop computers. The existence of at
least two stories suggests that the hackers wished to protect their
actual sources. In fact, some of the phone numbers had, to my certain
knowledge, appeared previously on bulletin boards.

   At this first stage, the hackers had no passwords; they could
simply call up the log-in page. Not being registered on that
computer, they were given the usual three tries before the line was

   For a while, the existence of these log-in pages was a matter of
mild curiosity.  Then, one day, in the last week of October, one of
the log-in pages looked different: it contained what appeared to be a
valid password, and one with system manager status, no less. A
satisfactory explanation for the appearance of this password
imprinted on a log-in page has not so far been forthcoming.  Perhaps
it was carelessness on the part of a BT engineer who thought that, as
the phone number was unlisted, no unauthorised individual would ever
see it.  The pass-number was tried and admission secured.

** Page 92

   After a short period of exploration of the database, which
appeared to be a 'snapshot' of Prestel rather than a live version of
it--thus showing that particular computer was not receiving constant
updates from Duke--the hackers decided to explore the benefits of
System Manager status. Since they had between them some freelance
experience of editing on Prestel, they knew that all Prestel special
features pages are in the *9nn# range: 910 for editing; 920 to change
personal passwords; 930 for mailbox messages and so ...what would
pages 940, 950, 960 and so on do? It became obvious that these pages
would reveal details of users together with account numbers
(systelnos), passwords and personal passwords.  There were facilities
to register and deregister users.

   However, all this was taking place on a non-public computer. Would
the same passwords on a 'live' Prestel machine give the same
benefits? Amazingly enough, the passwords gave access to every
computer on the Prestel network. It was now time to examine the user
registration details of real users as opposed to the BT employees who
were on the development machine. The hackers were able to assume any
personality they wished and could thus enter any Closed User Group,
simply by picking the right name. Among the CUG services they swooped
into were high-priced ones providing investment advice for clients of
the stockbroker Hoare Govett and commentary on international currency
markets supplied by correspondents of the Financial Times. They were
also able to penetrate Homelink, the telebanking service run by the
Nottingham Building Society.  They were not able to divert sums of
money, however, as Homelink uses a series of security checks which
are independent of the Prestel system.

   Another benefit of being able to become whom they wished was the
ability to read Prestel Mailboxes, both messages in transit that had
not yet been picked up by the intended recipient and those that had
been stored on the system once they had been read.  Among the
Mailboxes read was the one belonging to Prince Philip.  Later, with a
newspaper reporter as witness, one hacker sent a Mailbox, allegedly
from Prince Philip to the Prestel System Manager:

I do so enjoy puzzles and games. Ta ta. Pip! Pip!

                                     H R H Hacker

   Newspaper reports also claimed that the hackers were able to gain
editing passwords belonging to IPs, enabling them to alter pages and
indeed the Daily Mail of November 2nd carried a photograph of a
Prestel page from the Financial Times International Financial Alert

** Page 93

               FT NEWSFLASH!!!      1 EQUALS $50

   The FT maintained that, whatever might theoretically have been
possible, in fact they had no record of their pages actually being so
altered and hazarded the suggestion that the hacker, having broken
into their CUG and accessed the page, had 'fetched it back' onto his
own micro and then edited there, long enough for the Mail's
photographer to snap it for his paper, but without actually
retransmitting the false page back to Prestel. As with so many other
hacking incidents, the full truth will never be known because no one
involved has any interest in its being told.

   However, it is beyond doubt that the incident was regarded with the
utmost seriousness by Prestel itself. They were convinced of the
extent of the breach when asked to view page 1, the main index page,
which bore the deliberate mis-spelling: Idnex. Such a change
theoretically could only have been made by a Prestel employee with
the highest internal security clearance. Within 30 minutes, the
system manager password had been changed on all computers, public and
research. All 50,000 Prestel users signing on immediately after
November 2nd were told to change their personal password without
delay on every computer to which they were registered. And every IP
received, by Special Delivery, a complete set of new user and editing

   Three weeks after the story broke, the Daily Mail thought it had
found yet another Prestel hack and ran the following page 1 headline:
'Royal codebuster spies in new raid on Prestel', a wondrous
collection of headline writer's buzzwords to capture the attention of
the sleepy reader. This time an Information Provider was claiming
that, even after new passwords had been distributed, further security
breaches had occurred and that there was a 'mole' within Prestel
itself. That evening, Independent Television News ran a feature much
enjoyed by cognoscenti: although the story was about the Prestel
service, half the film footage used to illustrate it was wrong: they
showed pictures of the Oracle (teletext) editing facility and of
some-one using a keypad that could only have belonged to a TOPIC set,
as used for the Stock Exchange's private service. Finally, the name
of the expert pulled in for interview was mis-spelled although he was
a well-known author of micro books. The following day, BBC-tv's
breakfast show ran an item on the impossibility of keeping Prestel
secure, also full of ludicrous inaccuracies.

** Page 94

   It was the beginning of a period during which hackers and hacking
attracted considerable press interest. No news service operating in
the last two months of 1984 felt it was doing an effective job if it
couldn't feature its own Hacker's Confession, suitably filmed in deep
shadow. As happens now and again, press enthusiasm for a story ran
ahead of the ability to check for accuracy and a number of Hacks That
Never Were were reported and, in due course, solemnly commented on.

   BT had taken much punishment for the real hack--as well as causing
deep depression among Prestel staff, the whole incident had occurred
at the very point when the corporation was being privatised and
shares being offered for sale to the public--and to suffer an
unwarranted accusation of further lapses in security was just more
than they could bear.  It is unlikely that penetration of Prestel to
that extent will ever happen again, though where hacking is
concerned, nothing is impossible.

   There is one, relatively uncommented-upon vulnerability in the
present Prestel set-up: the information on Prestel is most easily
altered via the bulk update protocols used by Information Providers,
where there is a remarkable lack of security. All the system
presently requires is a 4-character editing password and the IP's
systel number, which is usually the same as his mailbox number
(obtainable from the on-system mailbox directory on page *7#) which
in turn is very likely to be derived from a phone number.

Other viewdata services

   Large numbers of other viewdata services exist: in addition to the
Stock Exchange's TOPIC and the other viewdata based services
mentioned in chapter 4, the travel trade has really clutched the
technology to its bosom: the typical High Street agent not only
accesses Prestel but several other services which give up-to-date
information on the take-up of holidays, announce price changes and
allow confirmed air-line and holiday bookings.

   Several of the UK's biggest car manufacturers have a stock locator
system for their dealers: if you want a British Leyland model with a
specific range of accessories and in the colour combinations of your
choice, the chances are that your local dealer will not have it
stock. He can, however, use the stock locator to tell him with which
other dealer such a machine may be found.

   Stock control and management information is used by retail chains
using, in the main, a package developed by a subsidiary of Debenhams.
Debenhams had been early enthusiasts of Prestel in the days when it
was still being pitched at a mass consumer audience--its service was
called Debtel which wags suggested was for people who owed money or,
alternatively, for upper-class young ladies.

** Page 95

   Later it formed DISC to link together its retail outlets, and this
was hacked in 1983.  The store denied that anything much had
happened, but the hacker appeared (in shadow) on a tv program
together with a quite convincing demonstration of his control over
the system.

   Audience research data is despatched in viewdata mode to
advertising agencies and broadcasting stations by AGB market
research.  There are even alternate viewdata networks rivalling that
owned by Prestel, the most important of which is, at the time of
writing, the one owned by Istel and headquartered at Redditch in the
Midlands. This network transports several different trade and
professional services as well as the internal data of British
Leyland, of whom Istel is a subsidiary.

   A viewdata front-end processor is a minicomputer package which
sits between a conventionally-structured database and its ports which
look into the phone-lines. Its purpose is to allow users with
viewdata sets to search the main database without the need to
purchase an additional conventional dumb terminal. Some view- data
front-end processors (FEPs) expect the user to have a full alphabetic
keyboard, and merely transform the data into viewdata pages 40
characters by 24 lines in the usual colours. More sophisticated FEPs
go further and allow users with only numeric keypads to retrieve
information as well. By using FEPs a database publisher or system
provider can reach a larger population of users. FEPs have been known
to have a lower standard of security protection than the conventional
systems to which they were attached.

Viewdata standards

   The UK viewdata standard--the particular graphics set and method
of transmitting frames -- is adopted in many other European countries
and in former UK imperial possessions. Numbers and passwords to
access these services occasionally appear on bulletin boards and the
systems are particularly interesting to enter while they are still on
trial. As a result of a quirk of Austrian law, anyone can
legitimately enter their service without a password; though one is
needed if you are to extract valuable information. However, important
variants to the UK standards exist: the French (inevitably) have a
system that is remarkably similar in outline but incompatible.

** Page 96

   In North America, the emerging standard which was originally put
together by the Canadians for their Telidon service but which has
now, with modifications, been promoted by Ma Bell, has high
resolution graphics because, instead of building up images from block
graphics, it uses picture description techniques (eg draw line, draw
arc, fill-in etc) of the sort relatively familiar to most users of
modern home micros. Implementations of NALPS (as the US standard is
called) are available for the IBM PC.

   The Finnish public service uses software which can handle nearly
all viewdata formats, including a near-photographic mode.

   Software similar to that used in the Finnish public service can be
found on some private systems.  Countries vary considerably in their
use of viewdata technology: the German and Dutch systems consist
almost entirely of gateways to third-party computers; the French
originally cost-justified their system by linking it to a massive
project to make all telephone directories open to electronic enquiry,
thus saving the cost of printed versions. French viewdata terminals
thus have full alpha-keyboards instead of the numbers-only versions
common in other countries. For the French, the telephone directory is
central and all other information peripheral. Teletel/Antiope, as the
service is called, suffered its first serious hack late in 1984 when
a journalist on the political/satirical weekly Le Canard Finchaine
claimed to have penetrated the Atomic Energy Commission's computer
files accessible via Teletel and uncovered details of laser projects,
nuclear tests in the South Pacific and an experimental nuclear

Viewdata: the future

   Viewdata grew up at a time when the idea of mass computer
ownership was a fantasy, when the idea that private individuals could
store and process data locally was considered far-fetched and when
there were fears that the general public would have difficulties in
tackling anything more complicated than a numbers- only key-pad.
These failures of prediction have lead to the limitations and
clumsiness of present-day viewdata. Nevertheless, the energy and
success of the hardware salesmen plus the reluctance of companies and
organisations to change their existing set-ups will ensure that for
some time to come, new private viewdata systems will continue to be
introduced...and be worth trying to break into.

   There is one dirty trick that hackers have performed on private
viewdata systems. Entering them is often easy, because high-level
editing passwords are, as mentioned earlier, sometimes desperately
insecure (see chapter 6) and it is easy to acquire editing status.

** Page 97

   Once you have discovered you are an editor, you can go to edit
mode and edit the first page on the system, page 0: you can usually
place your own message on it, of course; but you can also default all
the routes to page 90. Now *90# in most viewdata systems is the
log-out command, so the effect is that, as soon as someone logs in
successfully and tries to go beyond the first page, the system logs
them out....

   However, this is no longer a new trick, and one which should be
used with caution: is the database used by an important organisation?
Are you going to tell the system manager what you have done and
urge more care in password selection in future?

** Page 98


Radio Computer Data

   Vast quantities of data traffic are transmitted daily over the
radio frequency spectrum; hacking is simply a matter of hooking up a
good quality radio receiver and a computer through a suitable
interface. On offer are news services from the world's great press
agencies, commercial and maritime messages, meteorological data, and
plenty of heavily-encrypted diplomatic and military traffic. A
variety of systems, protocols and transmission methods are in use and
the hacker jaded by land-line communication (and perhaps for the
moment put off by the cost of phone calls) will find plenty of fun on
the airwaves.

   The techniques of radio hacking are similar to those necessary for
computer hacking. Data transmission over the airwaves uses either a
series of audio tones to indicate binary 0 and 1 which are modulated
on transmit and demodulated on receive or alternatively frequency
shift keying which involves the sending of one of two slightly
different radio frequency carriers, corresponding to binary 0 or
binary 1. The two methods of transmission sound identical on a
communications receiver (see below) and both are treated the same for
decoding purposes. The tones are different from those used on
land-lines--'space' is nearly always 1275 Hz and 'mark' can be one of
three tones: 1445 Hz (170 Hz shift--quite often used by amateurs and
with certain technical advantages); 1725 Hz (450 Hz shift--the one
most commonly used by commercial and news services) and 2125 Hz (850
Hz shift--also used commercially). The commonest protocol uses the
5-bit Baudot code rather than 7-bit or 8-bit ASCII. The asynchronous,
start/stop mode is the most common.  Transmission speeds include: 45
baud (60 words/minute), 50 baud (66 words/minute), 75 baud (100
words/ minute). 50 baud is the most common.  However, many
interesting variants can be heard--special versions of Baudot for
non- European languages, error correction protocols, and various
forms of facsimile.

   The material of greatest interest is to be found in the high
frequency or 'short wave' part of the radio spectrum, which goes from
2 MHz, just above the top of the medium wave broadcast band, through
to 30 MHz, which is the far end of the 10-meter amateur band which
itself is just above the well-known Citizens' Band at 27 MHz.

** Page 99

   The reason this section of the spectrum is so interesting is that,
unique among radio waves, it has the capacity for world-wide
propagation without the use of satellites, the radio signals being
bounced back, in varying degrees, by the ionosphere. This special
quality means that everyone wants to use HF (high frequency)
transmission--not only international broadcasters, the propaganda
efforts of which are the most familiar uses of HF. Data transmission
certainly occurs on all parts of the radio spectrum, from VLF (Very
Low Frequency, the portion below the Long Wave broadcast band which
is used for submarine communication), through the commercial and
military VHF and UHF bands, beyond SHF (Super High Frequency, just
above 1000 MHz) right to the microwave bands. But HF is the most
rewarding in terms of range of material available, content of
messages and effort required to access it.

   Before going any further, hackers should be aware that in a number
of countries even receiving radio traffic for which you are not
licensed is an offence; in nearly all countries making use of
information so received is also an offence and, in the case of news
agency material, breach of copyright may also present a problem.

   However, owning the equipment required is usually not illegal and,
since few countries require a special license to listen to amateur
radio traffic (as opposed to transmitting, where a license is needed)
and since amateurs transmit in a variety of data modes as well,
hackers can set about acquiring the necessary capability without


   The equipment required consists of a communications receiver, an
antenna, an interface unit/software and a computer.

Communications receiver - This is the name given to a good quality
high frequency receiver. Suitable models can be obtained,
second-hand, at around 100; new receivers cost upwards of 175.
There is no point is buying a radio simply designed to pick up
shortwave broadcasts which will lack the sensitivity, selectivity and
resolution necessary. A minimum specification would be:

Coverage      500 kHz--30 MHz

Resolution    >100 Hz

** Page 100

Modes         AM, Upper Side Band, Lower Side Band,
              CW (Morse)

   Tuning would be either by two knobs, one for MHz, one for kHz, or
by keypad.  On more expensive models it is possible to vary the
bandwidth of the receiver so that it can be widened for musical
fidelity and narrowed when listening to bands with many signals close
to one another.

   Broadcast stations transmit using AM (amplitude modulation), but
in the person-to-person contacts of the aeronautical, maritime and
amateur world, single-side-band-suppressed carrier techniques are
used--the receiver will feature a switch marked AM, USB, LSB, CW etc.
Side-band transmission uses less frequency space and so allows more
simultaneous conversations to take place, and is also more efficient
in its use of the power available at the transmitter. The chief
disadvantage is that equipment for receiving is more expensive and
must be more accurately tuned.  Upper side band is used on the whole
for voice traffic, and lower side band for data traffic. (Radio
amateurs are an exception: they also use lower side-band for voice
transmissions below 10 MHz.) Suitable sources of supply for
communications receivers are amateur radio dealers, whose addresses
may be found in specialist magazines like Practical Wireless, Amateur
Radio, Ham Radio Today.

Antenna - Antennas are crucial to good shortwave reception--the sort
of short 'whip' aerial found on portable radios is quite insufficient
if you are to capture transmissions from across the globe. When using
a computer close to a radio you must also take considerable care to
ensure that interference from the CPU and monitor don't squash the
signal you are trying to receive. The sort of antenna I recommend is
the 'active dipole', which has the twin advantages of being small and
of requiring little operational attention. It consists of a couple of
1-meter lengths of wire tied parallel to the ground and meeting in a
small plastic box. This is mounted as high as possible, away from
interference, and is the 'active' part. From the plastic box descends
coaxial cable which is brought down to a small power supply next to
the receiver and from there the signal is fed into the receiver
itself. The plastic box contains special low-noise transistors.

   It is possible to use simple lengths of wire, but these usually
operate well only on a limited range of frequencies, and you will
need to cover the entire HF spectrum. Active antennas can be obtained
by mail order from suppliers advertising in amateur radio
magazines--the Datong is highly recommended.

** Page 101

   Interface The 'interface' is the equivalent of the modem in landline
communications; indeed, advertisements of newer products actually refer to
radio modems. Radio tele-type, or RTTY, as it is called, is traditionally
received on a modified teleprinter or telex machine; and the early interfaces
or terminal units (TUs) simply converted the received audio tones into 'mark'
and 'space' to act as the equivalent of the electrical line conditions of a
telex circuit.  Since the arrival of the microcomputer, however, the design
has changed dramatically and the interface now has to perform the following

1 Detect the designated audio tones

2 Convert them into electrical logic states

3 Strip the start/stop bits, convert the Baudot code into ASCII
equivalents, reinsert start/stop bits

4 Deliver the new signal into an appropriate port on the computer.
(If RS232C is not available, then any other port, e.g. Game, that

   A large number of designs exist: some consist of hardware
interfaces plus a cassette, disc or ROM for the software; others
contain both the hardware for signal acquisition and firmware for its
decoding in one box.

   Costs vary enormously and do not appear to be related to quality
of result. The kit-builder with a ZX81 can have a complete set-up for
under 40; semi-professional models, including keyboards and screen
can cost in excess of 1000.

   The kit I use is based on the Apple II (because of that model's
great popularity in the USA, much hardware and software exists); the
interface talks into the game port and I have several items of
software to present Baudot, ASCII or Morse at will. There is even
some interesting software for the Apple which needs no extra
hardware--the audio from the receiver is fed direct into the cassette
port of the Apple, but this method is difficult to replicate on other
machines because of the Apple's unique method of reading data from

** Page 102

   Excellent inexpensive hard/firmware is available for many Tandy
computers, and also for the VlC20/Commodore 64. On the whole US
suppliers seem better than those in the UK or Japan-- products are
advertised in the US magazines QST and 73.

   Setting Up Particular attention should be paid to linking all the
equipment together; there are special problems about using sensitive
radio receiving equipment in close proximity to computers and VDUs.
Computer logic blocks, power supplies and the synchronising pulses on
VDUs are all excellent sources of radio interference (rfi). RFI
appears not only as individual signals at specific points on the
radio dial, but also as a generalised hash which can blank out all
but the strongest signals.

   Interference can escape from poorly packaged hardware, but also
from unshielded cables which act as aerials. The remedy is simple to
describe: encase and shield everything, connecting all shields to a
good earth, preferably one separate from the mains earth. In
practice, much attention must be paid to the detail of the
interconnections and the relative placing of items of equipment. In
particular, the radio's aerial should use coaxial feeder with a
properly earthed outer braid, so that the actual wires that pluck the
signals from the ether are well clear of computer-created rfi. It is
always a good idea to provide a communications receiver with a proper
earth, though it will work without one: if used with a computer, it
is essential.

   Do not let these paragraphs put you off; with care excellent
results can be obtained. And bear in mind my own first experience:
ever eager to try out same new kit, I banged everything together with
great speed--ribbon cable, poor solder joints, an antenna taped
quickly to a window in a metal frame less than two meters from the
communications receiver--and all I could hear from 500 kHz to 30
MHz, wherever I tuned, was a great howl-whine of protest...

Where to listen

   Scanning through the bands on a good communications receiver, you
realise just how crowded the radio spectrum is. The table in Appendix
VI gives you an outline of the sandwich-like fashion in which the
bands are organised.

   The 'fixed' bands are the ones of interest; more particularly, the
following ones are where you could expect to locate news agency
transmissions (in kHz):

** Page 103

3155     -- 3400                     14350   --   14990
3500     -- 3900                     15600   --   16360
3950     -- 4063                     17410   --   17550
4438     -- 4650                     18030   --   18068
4750     -- 4995                     18168   --   18780
5005     -- 5480                     18900   --   19680
5730     -- 5950                     19800   --   19990
6765     -- 7000                     20010   --   21000
7300     -- 8195                     21850   --   21870
9040     -- 9500                     22855   --   23200
ggoo     -- 9995                     23350   --   24890
10100    -- 11175                    25010   --   25070
11400    -- 11650                    25210   --   25550
12050    -- 12330                    26175   --   28000
13360    -- 13600                    29700   --   30005
13800    -- 14000

In addition, amateurs tend to congregate around certain spots on the
frequency map: 3590, 14090, 21090, 28090, and at VHF/UHF: 144.600,
145.300, MHz 432.600, 433.300.

Tuning In

   Radio Teletype signals have a characteristic two-tone warble sound
which you will hear properly only if your receiver is operating in
SSB (single-side-band) mode. There are other digital tone-based
signals to be heard: FAX (facsimile), Helschcrieber (which uses a
technique similar to dot-matrix printers and is used for Chinese and
related pictogram-style alphabets), SSTV (slow scan television, which
can take up to 8 seconds to send a low-definition picture), and

   But with practice, the particular sound of RTTY can easily be
recognised. More experienced listeners can also identify shifts and
speeds by ear.

   You should tune into the signal watching the indicators on your
terminal unit to see that the tones are being properly captured--
typically, this involves getting two LEDs to flicker simultaneously.

   The software will now try to decode the signal, and it will be up
to you to set the speed and 'sense'. The first speed to try is 66/7
words per minute, which corresponds to 50 baud, as this is the most
common. On the amateur bands, the usual speed is 60 words per minute
(45 baud); thereafter, if the rate sounds unusually fast, you try 100
words per minute (approximately 75 baud).

** Page 104

   By 'sense' or 'phase' is meant whether the higher tone corresponds
to logical 1 or logical 0.  Services can use either format; indeed
the same transmission channel may use one 'sense' on one occasion and
the reverse 'sense' on another. Your software can usually cope with
this. If it can't, all is not lost: you retune your receiver to the
opposite, side-band and the phase will thereby be reversed. So, if
you are listening on the lower side-band (LSB), usually the
conventional way to receive, you simply switch over to USB (upper
side-band), retune the signal into the terminal unit, and the sense'
will have been reversed.

   Many news agency stations try to keep their channels open even if
they have no news to put out: usually they do this by sending test
messages like: 'The quick brown fox....' or sequences like
'RYRYRYRYRYRY...' such signals are useful for testing purposes, if
a little dull to watch scrolling up the VDU screen.

   You will discover many signals that you can't decode: the
commonest reason is that the transmissions do not use European
alphabets, and all the elements in the Baudot code have been
re-assigned--some versions of Baudot use not one shift, but two, to
give the required range of characters. Straightforward en- crypted
messages are usually recognisable as coming in groups of five
letters, but the encryption can also operate at the bit- as well as
at the character-level -- in that case, too, you will get

   A limited amount of ASCII code as opposed to Baudot is to be
found, but mostly on the amateur bands.

   Finally, an error-correction protocol, called SITOR, is
increasingly to be found on the maritime bands, with AMTOR, an amateur
variant, in the amateur bands, SITOR has various modes of operation
but, in its fullest implementation, messages are sent in blocks which
must be formally acknowledged by the recipient before the next one is
despatched. The transmitter keeps trying until an acknowledgement is
received. You may even come across, on the amateur bands, packet
radio, which has some of the features of packet switching on digital
land lines. This is one of the latest enthusiasms in amateur radio
with at least two different protocols in relatively wide use.
Discussion of SITOR and packet radio is beyond the scope of this
book, but the reader is referred to BARTG (the British Amateur Radio
Teletype Group) and its magazine Datacom for further information. You
do not need to be a licensed radio amateur to join. The address is:
27 Cranmer Court, Richmond Road, Kingston KT2 SPY.

   Operational problems of radio hacking are covered at the end of
Appendix I, the Baudot code is given Appendix IV and an outline
frequency plan is to be found in Appendix VI.

** Page 105

   The material that follows represents some of the types of common
transmissions: news services, test slips (essentially devices for
keeping a radio channel open), and amateur. The corruption in places
is due either to poor radio propagation conditions or to the presence
of interfering signals.








** Page 106









** Page 107


Hacking: the Future

   Security is now probably the biggest single growth area within the
mainstream computer business. At conference after conference,
consultants compete with each other to produce the most frightening

   The main concern, however, is not hacking but fraud. Donn Parker,
a frequent writer and speaker on computer crime based at the Stanford
Research Institute has put US computer fraud at $3000 million a year;
although reported crimes amount to only $100 million annually. In
June 1983 the Daily Telegraph claimed that British computer-related
frauds could be anything between 500 million and 2.5 billion a
year. Detective Inspector Ken McPherson, head of the computer crime
unit at the Metropolitan Police, was quoted in 1983 as saying that
within 15 years every fraud would involve a computer. The trouble is,
very few victims are prepared to acknowledge their losses. To date,
no British clearing bank has admitted to suffering from an
out-and-out computer fraud, other than the doctoring of credit and
plastic ID cards. Few consultants believe that they have been immune.

   However, to put the various threats in perspective, here are two
recent US assessments. Robert P Campbell of Advanced Information
Management, formerly head of computer security in the US Army,
reckons that only one computer crime in 100 is detected; of those
detected, 15 per cent or fewer are reported to the authorities, and
that of those reported, one in 33 is successfully prosecuted--a
'clear-up' rate of one in 22,000.

   And Robert Courtney, former security chief at IBM produced a list
of hazards to computers: 'The No 1 problem now and forever is errors
and omissions'. Then there is crime by insiders, particularly
non-technical people of three types: single women under 35; 'little
old ladies' over 50 who want to give the money to charity; and older
men who feel their careers have left them neglected.  Next, natural
disasters. Sabotage by disgruntled employees. Water damage. As for
hackers and other outsiders who break in, he estimates it is less
than 3 per cent of the total.

** Page 108

   Here in the UK, the National Computing Centre says that at least
90 per cent of computer crimes involve putting false information into
a computer, as opposed to sophisticated logic techniques; such crimes
are identical to conventional embezzlement: looking for weaknesses
in an accounting system and taking advantage. In such cases the
computer merely carries out the fraud with more thoroughness than a
human, and the print-out gives the accounts a spurious air of being

   In the meantime, we are on the threshold of a new age of
opportunities for the hacker. The technology we can afford has
suddenly become much more interesting.

   The most recent new free magazines to which I have acquired
subscriptions are for owners of the IBM PC, its variants and clones.
There are two UK monthlies for regular users, another for corporate
buyers and several US titles.

   The IBM PC is only partly aimed at small business users as a
stand-alone machine to run accounting, word processing, spread- sheet
calculation and the usual business dross; increasingly the marketing
is pitching it as an executive work-station, so that the corporate
employee can carry out functions not only local to his own office,
but can access the corporate mainframe as well--for data, messaging
with colleagues, and for greater processing power.

   In page after page, the articles debate the future of this
development--do employees want work-stations? Don't many bosses still
feel that anything to do with typing is best left to their secretary?
How does the executive workstation relate to the mainframe? Do you
allow the executive to merely collect data from it, or input as well?
If you permit the latter, what effect will this have on the integrity
of the mainframe's files? How do you control what is going on? What
is the future of the DP professional? Who is in charge?

   And so the articles go on. Is IBM about to offer packages which
integrate mainframes and PCs in one enormous system, thus effectively
blocking out every other computer manufacturer and software publisher
in the world by sheer weight and presence?

   I don't know the answers to these questions, but elsewhere in
these same magazines is evidence that the hardware products to
support the executive workstation revolution are there--or, even if
one has the usual cynicism about computer trade advertising ahead of
actual availability, about to be.

   The products are high quality terminal emulators, not the sort of
thing hitherto achieved in software--variants on asynchronous
protocols with some fancy cursor addressing--but cards capable of
supporting a variety of key synchronous communications, like 327x
(bisynch and SDLC), and handling high-speed file transfers in CICs,

** Page 109

   These products feature special facilities, like windowing or
replicate aspects of mainframe operating systems like VM (Virtual
Machine), giving the user the experience of having several different
computers simultaneously at his command. Other cards can handle IBM's
smaller mini- mainframes, the Systems/34 and /38. Nor are other
mainframe manufacturers with odd-ball comms requirements ignored:
ICL, Honeywell and Burroughs are all catered for. There are even
several PC add-ons which give a machine direct X.25; it can sit on a
packet-switched network without the aid of a PAD.

   Such products are expensive by personal micro standards, but it
means that, for the expenditure of around 8000, the hacker can call
up formidable power from his machine. The addition of special
environments on these new super micros which give the owner direct
experience of mainframe operating systems--and the manuals to go with
them--will greatly increase the population of knowledgeable computer
buffs. Add to this the fact that the corporate workstation market, if
it is at all succesful, must mean that many executives will want to
call their mainframe from home --and there will be many many more
computer ports on the PTSN or sitting on PSS.

   There can be little doubt that the need for system security will
play an increasing role in the specification of new mainframe
installations. For some time, hardware and software engineers have
had available the technical devices necessary to make a computer
secure; the difficulty is to get regular users to implement the
appropriate methods--humans can only memorise a limited number of
passwords. I expect greater use will be made of threat monitoring
techniques: checking for sequences of unsuccessful attempts at
logging in, and monitoring the level of usage of customers for
extent, timing, and which terminals or ports they appear on.

   The interesting thing as far as hackers are concerned is that it
is the difficulty of the exercise that motivates us, rather than the
prospect of instant wealth. It is also the flavour of naughty, but
not outright, illegality. I remember the Citizens Band radio boom of
a few years ago: it started quietly with just a handful of London
breakers who had imported US sets, really simply to talk to a few
friends. One day everyone woke up, switched on their rigs and
discovered overnight there was a whole new sub-culture out there,
breathing the ether. Every day there were more and more until no
spare channels could be found. Then some talented engineers found out
how to freak the rigs and add another 40 channels to the original 40.
And then another 40. Suddenly there were wholesalers and retailers
and fanzines, all selling and promoting products the using or
manufacturing of which was illegal under British law.

** Page 110

   Finally, the government introduced a legalised CB, using different
standards from the imported US ones. Within six months the illegal
scene had greatly contracted, and no legal CB service of comparable
size ever took its place. Manufacturers and shop- keepers who had
expected to make a financial killing were left with warehouses full
of the stuff. Much of the attraction of AM CB was that it was
forbidden and unregulated. There is the desire to be an outlaw, but
clever and not too outrageous with it, in very many of us.

   So I don't believe that hacking can be stopped by tougher
security, or by legislation, or even by the fear of punishment.

   Don't get me wrong: I regard computers as vastly beneficial. But
they can threaten our traditional concepts of freedom, individuality
and human worth I like to believe hacking is a curious
re-assertion of some of those ideas.

   The challenge of hacking is deeply ingrained in many computer
enthusiasts; where else can you find an activity the horizons of
which are constantly expanding, where new challenges and dangers can
be found every day, where you are not playing a visibly artificial
'game', where so much can be accessed with so little resource but a
small keyboard, a glowing VDU, an inquisitive and acquisitive brain,
and an impish mentality?

** Page 111


Trouble Shooting

   The assumption is that you are operating in the default mode of
300/300 baud asynchronous using CCITT tones, 7 bits, even parity, one
stop bit, full-duplex/echo off, originate. You have dialled the
remote number, seized the line and can hear a data tone. Something is
not working properly. This is a partial list of possibilities.

The screen remains blank.

 * A physical link has failed -- check the cables between computer,
modem and phone line.

 * The remote modem needs waking up--send a <cr> or failing that, a
ENQ (<ctrl>E), character.

 * The remote modem is operating at a different speed.  Some modems
can be brought up to speed by hitting successive <cr>s; they usually
begin at 110 baud and then go to 300,so two successive <cr>s should
do the trick.

 * The remote modem is not working at V21 standards, either because
it is a different CCITT standard, e.g. V22, V22 bis, V23 etc or
operates on Bell (US) tones.

 * Since different standards tend to have different 'wake-up' tones
which are easily recognised with practice, you may be able to spot
what is happening. It shouldn't need to be said that if you are
calling a North American service you should assume Bell tones.

 * Both your modem and that of the remote service are in answer or in
originate and so cannot 'speak' to each other. Always assume you are
in the originate mode.

 * The remote service is not using ASCII/International Alphabet No 5.

The screen fills with random characters

 * Data format different from your defaults--check 7 or 8 bit
characters, even/odd parity, stop and start bits.

 * Mismatch of characters owing to misdefined protocol--check
start/stop, try alternately EOB/ACK and XON/XOF.

 * Remote computer operating at a different speed from you-- try, in
order, 110, 300, 600, 1200, 75.

** Page 112

 * Poor physical connection--if using an acoustic coupler check
location of handset, if not, listen on line to see if it is noisy or

 * The remote service is not using ASCII/International Alphabet No 5.

Every character appears twice

 * You are actually in half-duplex mode and the remote computer as
well as your own are both sending characters to your screen--switch
to full-duplex/echo off.

All information appears on only one line, which is constantly

 * The remote service is not sending line feeds--if your terminal
software has the facility, enable it to induce line feeds when each
display line is filled.  Many on-line services and public dial-up
ports let you configure the remote port to send line feeds and vary
line length. Your software may have a facility to show control
characters, in which case you will see <ctrl>J if the remote service
is sending line feeds.

Wide spaces appear between display lines.

* The remote service is sending line feeds and your software is
inducing another one simultaneously--turn off your induced carriage
return facility. In 'show control character' mode, you will see

Display lines are broken awkwardly

* The remote service is expecting your screen to support more
characters than it is able. Professional services tend to expect 80
characters across whilst many personal computers may have less than
40, so that they can be read on a tv screen. Check if your software
can help, but you may have to live with it.  Alternatively, the
remote computer may let you reconfigure its character stream.

Most of the display makes sense, but every so often it becomes

 * You have intermittent line noise--check if you can command the
remote computer to send the same stream again and see if you get the

 * The remote service is sending graphics instructions which your
computer and software can't resolve.

** Page 113

The display contains recognisable characters in definite groupings,
but otherwise makes no sense The data is intended for an intelligent
terminal, which will combine the transmitted data with a local
program so that it makes sense.

 * The data is intended for batch processing.

 * The data is encrypted Although the stream of data appeared
properly on your vdu, when you try to print it out, you get
corruption and over-printing

 * Most printers use a series of special control characters to enable
various functions--line feeds, back-space, double- intensity, special
graphics etc.  The remote service is sending a series of control
characters which, though not displayed on your screen, are
'recognised' by your printer, though often in not very helpful ways.
You may be able to correct the worst problems in software, e.g. by
enabling line-feeds; alternatively many printers can be re-configured
in hardware by appropriate settings of DIL switches internally.

When accessing a viewdata service, the screen fills with squares.

 * The square is the standard display default if your viewdata
terminal can't make sense of the data being sent to it.

 * Check physical connections and listen for line noise.

 * The viewdata host does not work to UK viewdata standards-- French
viewdata uses parallel attributes and has a number of extra features.
The CEPT standard for Europe contains features from both the UK and
French systems and you may be able to recognise some of the display.
North American videotex is alpha-geometric and sends line drawing
instructions rather than characters.

 * The viewdata host has enhanced graphics features, perhaps for
dynamically redefined character sets, alphageometric instructions, or
alpha-photographic (full resolution) pictures. If the host has some
UK standard-compatible features, you will be able to read them
normally. If the cursor jumps about the screen, the host has dynamic
graphics facilities. If the viewdata protocol is anything at all like
the UK standard, you should see regular clear-screens as each new
page comes up; however, advanced graphics features tend to work by
suppressing clear-screens.

** Page 114

 * The service you have dialled is not using viewdata. PSS is
accessible at 75/1200, as are one or two direct-dial services. In
this case you should be seeing a conventional display or trying one
of the other suggestions in this appendix. It is usual to assume that
any subscriber dialling into a 75/1200 port has only a 40 character

You can't see what you are typing

 * The remote computer is not echoing back to you--switch to
half-duplex. If the remote computer's messages now appear doubled;
that would be unusual but not unique; you will have to toggle back to
full-duplex for receive.

Data seems to come from the remote computer in jerky bursts rather
than as a smooth stream.

 * If you are using PSS or a similar packet-switched service and it
is near peak business hours either in your time zone or in that of
the host you are accessing, the effect is due to heavy packet
traffic. There is nothing you can do--do not send extra commands to
'speed things up' as those commands will arrive at the host
eventually and cause unexpected results.

 * The host is pausing for a EOB/ACK or XON/XOF message-- check your
protocol settings--try sending ctrl-Q or ctrl-F.

You have an apparently valid password but it is not accepted.

 * You don't have a valid password, or you don't have all of it.

 * The password has hidden control characters which don't display on
the screen. Watch out for <ctrl>H -- the back-space, which will
over-write an existing displayed character.

 * The password contains characters which your computer doesn't
normally generate--check your terminal software and see if there is a
way of sending them.

Most of the time everything works smoothly, but you can't get past
certain prompts

 * The remote service is looking for characters your computer doesn't
normally generate. Check your terminal software and see if there is a
way of sending them.

A list or file called up turns out to be boring--can you stop it?

 * Try sending <ctrl>S; this may simply make the remote machine
pause, until a <ctrl>Q is sent--and you may find the list resumes
where it left off. On the other hand it may take you on to a menu.

 * Send a BREAK signal (<ctrl>1). If one BREAK doesn't work, send
another in quick succession.

** Page 115

You wish to get into the operating system from an applications

 * Don't we all? There is no standard way of doing this, and indeed
it might be almost impossible, because the operating system can only
be addressed by a few privileged terminals, of which yours (and its
associated password) is not one.  However, you could try the

 * Immediately after signing on, send two BREAKs (<ctrl>1).

 * Immediately after signing on, try combinations of ESC, CTRL and
SHIFT. As a desperate measure, send two line feeds before signing
on--this has been known to work!.

 * At an options page, try requesting SYSTEM or some obvious
contraction like SYS or X. If in the Basic language, depending on the
dialect, SYSTEM or X in immediate mode should get you the operating

You are trying to capture data traffic from a short-wave radio and are having
little success

 * Your computer could be emitting so much radio noise itself that
any signal you are attempting to hear is squashed. To test: tune your
radio to a fairly quiet short-wave broadcast and then experiment
listening to the background hash with the computer switched first
on, then off. If the noise level drops when you turn off the
computer, then you need to arrange for more rf suppression and to
move the computer and radio further apart. Another source of rf noise
is the sync scan in a tv tube.

 * If you can hear the two-tones of rtty traffic but can't get
letters resolved, check that your terminal unit is locking on to the
signal (often indicated by LEDs); you should then at least get some
response on your screen, if it doesn't make immediate sense.

 * Once you have letters on screen, try altering the speed at which
you are receiving (see chapter 10); check also that you are reading
in the right 'sense', ie that mark and space have not been reversed.

 * In addition to signals sent with the conventional International
Telegraphic Code No 2 (Baudot), variants exist for foreign letter
sets, like Cyrillic, which your software may not be able to resolve.

 * There are other data-type services which sound a little like RTTY,
but are not: they include FAX (facsimile) hellschreiber ( a form of
remote dot-matrix printing), SITOR (see chapter 10) and special
military/diplomatic systems.

** Page 116



This glossary collects together the sort of name, word, abbreviation
phrase you could come across during your network adventures
and for which you may not be able to find a precise definition

Non--printing character used in some comms protocols to indicate that
a block has been received and that more can be sent; used in
association with EOB.

American National Standards Institute--one of a number of standards

Answer mode
When a modem is set up to receive calls--the usual mode for a host.
The user's computer will be in originate.

Automatic Repeat Request--method of error correction.

American Standard Code for Information Interchange--alternate name
for International Telegraph Alphabet No 5: 7-bit code to symbolise
common characters and comms instructions, usually transmitted as
8-bit code to include a parity bit.

Automatic Send Receive--any keyboard terminal capable of generating a
message into off-line storage for later transmission; includes
paper-tape telex machines as well as microcomputers.

Description of communications which rely on 'start' and 'stop' bits
to synchronise originator and receiver of data--hence asynchrnous
protocols, channels, modems, terminals etc.

** Page 117

Backward channel
Supervisory channel, not used as main channel of communication; in
viewdata the 75 baud back from the user to the host.

Measure of the signalling rate on a data channel, number of
signalling elements per second.

Modulation is direct on the comms line rather than using audio or
radio frequencies; used in some local area networks. A baseband or
'short-haul' modem can be used to link computers in adjacent offices,
but not over telephone lines.

5-bit data code used in telegraphy, telex and RTTY--also known as
International Telegraph Alphabet No 2.

(1) non-printing character which sounds a bell or bleep, usually
enabled by <ctrl> G; (2) Common name for US phone company and, in
this context, specifiers for a number of data standards and services,
e.g. Bell 103a, 202a, 212a, etc--see Appendix V

Bit Binary digit
value 0 or 1.

Broadband data channels have a wider bandwidth than ordinary
telephone circuits--12 times in fact, to give a bandwidth of 48kHz,
over which may simultaneous high-speed data transfers can take place.

Broadcast service
Data service in which all users receive the same information
simultaneously, without the opportunity to interrogate or query;
e.g. news services like AP, Reuters News, UPI etc. See also on-line

IBM protocol involving synchronous transmission of binary coded data.

** Page 118

British Library Automated Information Service-- substantial
bibliographic on-line host.

Non-printing character used in some data transmission protocols and
found on some terminals--can often be regenerated by using <ctrl> 1.

Binary Synchronous Communications--see bisynchronous.

I Byte
Group of bits (8) representing one data character.

Call accept
In packet-switching, the packet that confirms the party is willing to
proceed with the call.

Call redirection
In packet-switching, allows call to be automatically redirected from
original address to another, nominated address.

Call request
In packet-switching, packet sent to initiate a datacall.

Comite Consultatif International Telephonique et Telegraphique
--committee of International Telecommunications Union which sets
international comms standards. Only the US fails to follow its
recommendations in terms of modem tones, preferring 'Bell' tones. The
CCITT also sets such standards as V21, 24, X25 etc.

Character terminal
In packet-switching, a terminal which can only access via a PAD.

When two or more terminals are connected to a data channel at a
single point.

Common Carrier
A telecommunications resource providing facilities to the public.

** Page 119

Length of time connected to a remote computer, often the measure of
payment.  Contrast with cpu time or cpu units, which measures how
much 'effort' the host put into the communication.

Characters Per Second.

Cpu Time
In an on-line session, the amount of time the central processor
actually spends on the interaction process, as opposed to connect-
time; either can be used as the basis of tariffing.

Cyclic Redundancy Check--error detection method.

Closed User Group--group of users/terminals who enjoy privacy with
respect to a public service.

In packet-switching, an ordinary call, sometimes called a 'switched
virtual call'.

In packet-switching, dedicated line between customer's terminal and
packet-switch exchange (PSE).

Data Circuit-terminating Equipment--officialese for modems.

Data Terminal Equipment--officialese for computers.

Extended Binary Coded Decimal Interchange Code--IBM's alternative to
ASCII, based on an 8-bit code, usually transmitted synchronously. 256
characters are available.

Software/hardware set-up which makes one device mimic another, e.g. a
personal computer may emulate an industry-standard dumb terminal like
the VT100.  Compare simulator, which gives a device the attributes of
another, but not necessarily in real time, e.g. when a large mini
carries a program making it simulate another computer to develop

** Page 120

European direct access information network.

BT's name for its data services, covering both the equipment and the
type of line, e.g. Datel 100 corresponds to telegraph circuits, Datel
200 is the usual 300/300 asynchronous service, Datel 400 is for
one-way transmissions e.g.  monitoring of remote sites, Datel 600 is
a two- or four-wire asynchronous service at up to 1200 baud, Datel
2400 typically uses a 4-wire private circuit at 2400 baud
synchronous, etc. etc.

Data Encryption Standard--a US-approved method of encrypt- ing data
traffic, and somewhat controversial in its effectiveness.

Well-established on-line host available world-wide covering an
extensive range of scientific, bibiographic and news services. Also
known as Lockheed Dialog.

Call initiated via PTSN, no matter where it goes after that; as
opposed to service available via permanent leased line.

Transmission in two directions simultaneously, sometimes called
full-duplex; contrast half-duplex, in which alternate transmissions
by either end are required. NB this is terminology used in data
communications over land-lines.  Just to confuse matters, radio
technology refers to simplex, when only one party can transmit at a
time and a single radio frequency is used; two-frequency-simplex or
half-duplex when only one party can speak but two frequencies are
used, as in repeater and remote base working; and full-duplex, when
both parties can speak simultaneously and two radio frequencies are
used, as in radio-telephones.

(1) When a remote computer sends back to the terminal each letter as
it is sent to it for confirming re-display locally. (2) Effect on
long comms lines caused by successive amplifications
--echo-suppressors are introduced to prevent disturbance caused by
this phenomenon, but in some data transmission the echo- suppressors
must be switched off.

** Page 121

Electronic Industries Association, US standards body.

Non-printing character signifying 'who are you?' and often sent by
hosts as they are dialled up. When the user's terminal receives ENQ
it may be programmed to send out a password automatically.
Corresponds to <esc> E.

End Of Block--non-printing character used in some protocols, usually
in association with ACK.

Method of compensation for distortion over long comms channels.

Frequency Division Multiplexing--a wide bandwidth transmission
medium, e.g.  coaxial cable, supports several narrow band- width
channels by differentiating by frequency; compare time division

Frequency Shift Keying--a simple signalling method in which
frequencies but not phase or amplitude are varied according to
whether '1' or '0' is sent--used in low-speed asynchronous comms both
over land-line and by radio.

Hardware and software rules for remote devices to communicate with
each other, supervisory signals such as 'wait', 'acknowledge',
'transmit', 'ready to receive' etc.

In packet-switching, High Level Data Link Control procedure, an
international standard which detects and corrects errors in the
stream of data between the terminal and the exchange--and to provide
flow control.  Host The 'big' computer holding the information the
user wishes to retrieve.

** Page 122

Scientific on-line service from Pergamon.

see sideband.

International Standards Organisation.

Local Area Network--normally using coaxial cable, this form of
network operates at high speed over an office or works site, but no
further. May have inter-connect facility to PTSN or PSS.

Line Feed--cursor moves active position down one line--usual code is
<ctrl>J; not the same as carriage return, which merely sends cursor
to left-hand side of line it already occupies. However, in many
protocols/terminals/set-ups, hitting the <ret> or <enter> button
means both <lf> and <cr>.

Logical Channel
Apparently continuous path from one terminal to another.

see sideband.

Keyboard Send Receive--terminal with keyboard on which anything that
is typed is immediately sent. No off-line preparation facility, e.g.
teletypewriter, 'dumb' terminals.

Macro software
Facility frequently found in comms programs which permits the
preparation and sending of commonly-used strings of information,
particularly passwords and routing instructions.

One of the two conditions on a data communications line, the other
being 'space'; mark indicates 'idle' and is used as a stop bit.

** Page 123

Message switching
When a complete message is stored and then forwarded, as opposed to a
packet of information. This technique is used in some electronic mail
services, but not for general data transmission.


Device which divides a data channel into two or more independent
channels .

Multiple Virtual Storage--IBM operating system dating from mid-70s.

Network User Address, number by which each terminal on a
packet-switch network is identified (character terminals don't have
them individually, because they use a PAD). In PSS, it's a 10-digit

Network User Identity, used in PSS for dial-up access by each user.

In packet-switching, 8 consecutive bits of user data, e.g. 1

On-line service
Interrogative or query service available for dial-up. Examples
include Lockheed Dialog, Blaise, Dow Jones News Retrieval, etc;
leased-line examples include Reuters Monitor, Telerate.

Mode-setting for a modem operated by a user about to call another

Open Systems Interconnect--intended world standard for digital
network connections--c.f. SNA.  Packet terminal Terminal capable of
creating and disassembling packets, interacting with a
packet-network, c.f. character terminal.

** Page 124

Packet Assembly/disassembly Device--permits 'ordinary' terminals to
connect to packet switch services by providing addressing, headers,
(and removal), protocol conversion etc.

Parity checking
Technique of error correction in which one bit is added to each data
character so that the number of bits is always even (or always odd).

PDP/8 & /11
Large family of minis, commercially very sucessful, made by DEC.  the
PDP 8 was 12-bit, the PDP 11 is 16-bit. The LSI 11 have strong family
connections to the PDP 11, as have some configurations of the
desk-top Rainbow.

Method of controlling terminals on a clustered data network, where
each is called in turn by the computer to see if it wishes to
transmit or receive.

Agreed set of rules.

Packet Switch Exchange--enables packet switching in a network.

Public Switched Telephone Network--the voice-grade telephone network
dialled from a phone. Contrast with leased lines, digital networks,
conditioned lines etc.

jargon for the publicly-owned telecommunications authority/ utility

Permanent Virtual Circuit--a connection in packet switching which is
always open, no set-up required.

** Page 125

Redundancy checking
Method of error correction.

The list of definitions for interchange circuit: the US term for
CCITT V24--see Appendix III.

Popular operating system for PDP/11 family.

Radio Teletype -- method of sending telegraphy over radio waves.

Back-space deleting character, using <ctrl>H.

Secondary channel
Data channel, usually used for supervision, using same physical path
as main channel; in V23 which is usually 600 or 1200 baud
half-duplex, 75 baud traffic is supervisory but in viewdata is the
channel back from the user to the host, thus giving low-cost full

Chargeable unit of volume on PSS.

Serial transmission
One bit at a time, using a single pair of wires, as opposed to
parallel transmission, in which several bits are sent simultaneously
over a ribbon cable. A serial interface often uses many more than two
wires between computer and modem or computer and printer, but only
two wires carry the data traffic, the remainder being used for
supervision, electrical power and earthing, or not at all.

In radio the technique of suppressing the main carrier and limiting
the transmission to the information-bearing sideband. To listen at
the receiver, the carrier is re-created locally. The technique, which
produces large economies in channel occupany, is extensively used in
professional, non-broadcast applications. The full name is single
side-band, supressed carrier. Each full carrier supports two
sidebands, an upper and lower, USB and LSB respectively; in general,
USB is used for speech, LSB for data, but this is only a
convention--amateurs used LSB for speech below 10 MHz, for example.
ISB, independent side-band, is when the one carrier supports two
sidebands with separate information on them, usually speech on one
and data on the other. If you listen to radio teletype on the 'wrong'
sideband, 'mark' and 'space' values become reversed with a consequent
loss of meaning.

** Page 126

Error-correction protocol for sending data over radio-path using
frequent checks and acknowledgements.

System Network Architecture-- IBM proprietary networking protocol,
the rival to OSI.

One of two binary conditions in a data transmission channel, the
other being 'mark'. Space is binary 0.

Simultaneous Peripheral Operation On-Line--more usually, the ability,
while accessing a database, to store all fetched information in a
local memory buffer, from which it may be recalled for later
examination, or dumped to disc or printer.

Asynchronous transmission; the 'start' and 'stop' bits bracket each
data character.

Statistical Multiplexer
A statmux is an advanced multiplexer which divides one physical link
between several data channels, taking advantage of the fact that not
all channels bear equal traffic loads.

Start Text--non-printing character used in some protocols.

Switched Virtual Circuit--in packet switching, when connection
between two computers or computer and terminal must be set up by a
specific call.

** Page 127

Non-printing character often used in synchronous transmission to tell
a remote device to start its local timing mechanism.

Data transmission in which timing information is super-imposed ~,n
pure data.  Under this method 'start/stop' techniques are not used
and data exchange is more efficient, hence synchronous channel,
modem, terminal, protocol etc.

Time Division Multiplex--technique for sharing several data channels
along one high-grade physical link. Not as efficient as statistical

US packet-switch common carrier.

High-speed replacement for telex, as yet to find much commercial

Use of vertical blanking interval in broadcast television to transmit
magazines of text information, e.g. BBC's Ceefax and IBA's Oracle.

Public switched low-speed telegraph network.

The Stock Exchange's market price display service; it comes down a
leased line and has some of the qualities of both viewdata and

US packet-switch common carrier.

Set of recommendations by CCITT--see Appendix III.

Super-mini family made by DEC; often uses Unix operating system.

** Page 128

Technology allowing large numbers of users to access data easily on
terminal based (originally) on modified tv sets.  Information is
presented in 'page' format rather than on a scrolling screen and the
user issues all commands on a numbers-only keypad.  Various standards
exist of which the UK one is so far dominant; others include the
European CEPT standard which is similar to the UK one, a French
version and the US Presentation Level Protocol.  Transmission speeds
are usually 1200 baud from the host and 75 baud from the user.
Viewdata together with teletext is known jointly as videotex(t).

In the present context, a virtual drive, store, machine etc is one
which appears to the user to exist, but is merely an illusion
generated on a computer; thus several users of IBM's VM operating
system each think they have an entire separate computer, complete
with drives, discs and other peripherals--in fact the one actual
machine can support several lower-level operating systems

Industry-standard general purpose computer terminals with no storage
capacity or processing power but with the ability to be locally
programmed to accept a variety of asynchronous transmission
protocols--manufactured by DEC. The series has developed since the

Set of recommendations by CCITT--see Appendix III.

Pair of non-printing characters sometimes used in protocols to tell
devices when to start or stop sending. XON often corresponds to
<ctrl>Q and XOF to <ctrl>S.

Type of circuit used for telex and telegraphy--mark and space are
indicated by conditions of--or + 80 volts. Also known in the UK as
Tariff J. Usual telex speed is 50 baud, private wire telegraphy (news
agencies etc) 75 baud.

** Page 129


Selected CCITT Recommendations

V series: Data transmission over telephone circuits
V1        Power levels for data transmission over telephone lines
V3        International Alphabet No S (ASCII)
V4        General structure of signals of IA5 code for data
          transmission over public telephone network
V5        Standardisation of modulation rates and data signalling
          rates for synchronous transmission in general switched
V6        Ditto, on leased circuits
V13       Answerback simulator
V15       Use of acoustic coupling for data transmission
V19       Modems for parallel data transmission using telephone
          signalling frequencies
V20       Parallel data transmission modems standardised for
          universal use in the general switched telephone network
V21       200 baud modem standardised
V22       1200 bps full-duplex 2-wire modem for PTSN
V22bis    2400 bps full-duplex 2-wire modem for PTSN
V23       600/1200 bps modem for PTSN
V24       List of definitions for interchange circuits between data
          terminal equipment and data circuit-terminating equipment
V25       Automatic calling and/or answering equipment on PTSN
V26       2400 bps modem on 4-wire circuit
V26bis    2400/1200 bps modem for PTSN
V27       4800 bps modem for leased circuits
V27bis    4800 bps modem (equalised) for leased circuits
V27       4800 bps modem for PTSN
V29       9600 bps modem for leased circuits
V35       Data transmission at 48 kbits/sec using 60-108 kHz band

** Page 130

X      series: recommendations covering data networks
X1     International user classes of services in public data networks
X2     International user facilities in public data networks
X3     Packet assembly/disassembly facility (PAD)
X4     General structure of signals of IA5 code for transmission
       over public data networks
X20    Interface between data terminal equipment and data
       circuit-terminating equipment for start-stop transmission
       services on public data networks
X20bis V21-compatible interface
X21    Interface for synchronous operation
X25    Interface between data terminal equipment and data
       circuit-terminating equipment for terminals operating in
       the packet-switch mode on public data networks
X28    DTE/DCE interface for start/stop mode terminal equipment
       accessing a PAD on a public data network
X29    Procedures for exchange of control information and user
       data between a packet mode DTE and a PAD
X95    Network parameters in public data networks
X96    Call progress signals in public data networks
X121   International addressing scheme for PDNs

** Page 131


Computer Alphabets

   Four alphabets are in common use for computer communications:
ASCII, also known as International Telegraphic Alphabet No 5; Baudot,
used in telex and also known as International Telegraphic Alphabet No
2; UK Standard videotex, a variant of ASCII; and EDCDIC, used by IBM.

This is the standard, fully implemented character set. There are a
number of national variants: # in the US variant is  in the UK
variant. Many micro keyboards cannot generate all the characters
directly, particularly the non-printing characters used for control
of transmission, effectors of format and information separators.  The
'keyboard' column gives the usual method of providing them, but you
should check the firmware/software manuals for your particular
set-up. You should also know that many of the 'spare' control
characters are often used to enable special features on printers.

HEX    DEC ASCII Name               Keyboard  Notes

00      0  NUL Null                 ctrl @
01      1  SOH Start heading        ctrl A
02      2  STX Start text           ctrl B
03      3  ETX End text             ctrl C
04      4  EOT End transmission     ctrl D
05      5  ENQ Enquire              ctrl E
06      6  ACK Acknowledge          ctrl F
07      7  BEL  Bell                ctrl G
08      8  BS   Backspace           ctrl H    or special key
09      9  HT   Horizontal tab      ctrl I    or special key
OA     10  LF   Line feed           ctrl J
OB     11  VT   Vertical tab        ctrl K
0C     12  FF   Form feed           ctrl L

** Page 132

OD     13  CR Carriage return       ctrl M    or special key
OE     14  SO Shift out             ctrl N
OF     15  Sl Shift in              ctrl O
10     16  DLE Data link escape     ctrl P
11     17  DC1 Device control 1     ctrl Q    also XON
12     18  DC2 Device control 2     ctrl R
13     19  DC3 Device control 3     ctrl S    also XOF
14     20  DC4 Device control 4     ctrl T
15     21  NAK Negative acknowledge ctrl U
16     22  SYN Synchronous Idle     ctrl V
17     23  ETB End trans. block     ctrl W
18     24  CAN Cancel               ctrl X
19     25  EM End medium            ctrl Y
1A     26  SS Special sequence      ctrl Z    spare
1B     27  ESC Escape                         check manuals to
1C     28  FS File separator
1D     29  GS Group separator
1E     30  RS Record separator
1F     31  US Unit separator
20     32  SP Space
21     33  ~
22     34  "
23     35  #                                             
24     36  $
25     37  %
26     38  &
27     39  ' Apostrophe
28     40  (
29     41  )
2A     42  ~
2B     43  +
2C     44  , Comma
2D     45  -
2E     46  . Period
2F     47  / Slash
30     48  0
31     49  1
32     50  2
33     51  3
34     52  4
35     53  5
36     54  6
37     55  7

** Page 133

38     56  8
39     57  9
3A     58  : Colon
3B     59  ; Semicolon
3C     60  < 
3D     61
3E     62  >
3F     63  ?
40     64  @
41     65  A
42     66  B 
43     67  C
44     68  D
45     69  E
46     70  F
47     71  G
48     72  H
49     73  1
4A     74  J
4B     75  K
4C     76  L
4D     77  M
4E     78  N
4F     79  O
50     80  P
51     81  Q
52     82  R
53     83  S
54     84  T
55     85  U
56     86  V
57     87  W
58     88  X
59     89  Y
5A     90  Z  
5B     91  [
5C     92  \ Backslash
5D     93  1
5E     94  ^ Circumflex
5F     95  _ Underscore
60     96    Grave accent
61     97  a
62     98  b

** Page 134

63     99  c
64    100  d
65    101  e
66    102  f
67    103  9
68    104  h
69    105  i
6A    106  j
6B    107  k
6C    108  l
6D    109  m
6E    110  n
6F    111  o
70    112  p
71    113  q
72    114  r
73    115  s
74    116  t
75    117  u
76    118  v
77    119  w
78    120  x
79    121  y
7A    122  z
7B    123  {
7C    124
7D    125  }
7E    126  ~ Tilde
7F    127  DEL Delete

This is the telex/telegraphy code known to the CCITT as International
Alphabet No 2. It is essentially a 5-bit code, bracketed by a start
bit (space) and a stop bit (mark). Idling is shown by 'mark'. The
code only supports capital letters, figure and two 'supervisory'
codes: 'Bell' to warn the operator at the far end and 'WRU'--'Who are
you?' to interrogate the far end 'Figures' changes all characters
received after to their alternates and 'Letters' switches back. The
letters/figures shift is used to give the entire character set.

** Page 135

This is the character set used by the UK system, which is the most
widely used, world-wide. The character-set has many features in
common with ASCII but also departs from it in significant ways,
notably to provide various forms of graphics, colour controls,
screen-clear (ctrl L) etc. The set is shared with teletext which in
itself requires further special codes, e.g. to enable sub-titling to
broadcast television, news flash etc.  If you are using proper
viewdata software, then everything will display properly; if you are
using a conventional terminal emulator then the result may look
confusing.  Each character consists of 10 bits:

Start                      binary 0
7 bits of character code
Parity bit                 even
Stop                       binary 1

ENQ (Ctrl E) is sent by the host on log-on to initiate the
auto-log-on from the user's terminal. If no response is obtained, the
user is requested to input the password manually. Each new page
sequence opens with a clear screen instruction (Ctrl L, CHR$12)
followed by a home (Ctrl M, CHR$14).

Some viewdata services are also available via standard asynchronous
300/300 ports (Prestel is, for example); in these cases, the graphics
characters are stripped out and replaced by ****s; and the pages will
scroll up the screen rather than present themselves in the
frame-by-frame format.

** Page 136

*** Original contains a diagram of Viewdata Graphic Character Set.

** Page 137

   If you wish to edit to a viewdata system using a normal keyboard,
or view a viewdata stream as it comes from a host using
'control-show' facilities, the table below gives the usual
equivalents. The normal default at the left-hand side of each line is
alphanumeric white. Each subsequent 'attribute', i.e. if you wish to
change to colour, or a variety of graphics, occupies a character
space. Routing commands and signals to start and end edit depend on
the software installed on the viewdata host computer: in Prestel
compatible systems, the edit page is *910#, options must be entered
in lower case letters and end edit is called by <esc>K.

esc A        alpha red            esc Q     graphics red
esc B        alpha green          esc R     graphics green
esc C        alpha yellow         esc S     graphics yellow
esc D        alpha blue           esc T     graphics blue
esc E        alpha magenta        esc U     graphics magenta
esc F        alpha cyan           esc V     graphics cyan
esc G        alpha white          esc W     graphics white
esc H        flash                esc I     steady
esc L        normal height        esc M     double height
esc Y        contiguous graphics  esc Z     separated graphics

esc ctrl D   black background     esc-shift M new background
esc J        start edit           esc K end edit

The Extended Binary Coded Decimal Interchange Code is a 256-state
8-bit extended binary coded digit code employed by IBM for internal
purposes and is the only important exception to ASCII. Not all 256
codes are utilised, being reserved for future expansion, and a number
are specially identified for application- specific purposes. In
transmission, it is usual to add a further digit for parity checking.
Normally the transmission mode is synchronous, so there are no
'start' and 'stop' bits.  The table shows how EBCDIC compares with
ASCII of the same bit configuration.

** Page 138

IBM control characters:

EBCDIC     bits         Notes

NUL        0000  0000   Nul
SOH        0000  0001   Start of Heading
STX        0000  0010   Start of Text
ETX        0000  0011   End of Text
PF         0000  0100   Punch Off
HT         0000  0101   Horizontal Tab
LC         0000  0110   Lower Case
DEL        0000  0111   Delete
           0000  1000
RLF        0000  1001   Reverse Line Feed
SMM        0000  1010   Start of Manual  Message
VT         0000  1011   Vertical Tab
FF         0000  1100   Form Feed
CR         0000  1101   Carriage Return
SO         0000  1110   Shift Out
Sl         0000  1111   Shift In
DLE        0001  0000   Data Link Exchange
DC1        0001  0001   Device Control 1
DC2        0001  0010   Device Control 2
TM         0001  0011   Tape Mark
RES        0001  0100   Restore
NL         0001  0101   New Line
BS         0001  0110   Back Space
IL         0001  0111   Idle
CAN        0001  1000   Cancel
EM         0001  1001   End of Medium
CC         0001  1010   Cursor Control
CU1        0001  1011   Customer Use 1
IFS        0001  1100   Interchange File Separator
IGS        0001  1101   Interchange Group Separator
IRS        0001  1110   Interchange Record Separator
IUS        0001  1111   Interchange Unit Separator
DS         0010  0000   Digit Select
SOS        0010  0001   Start of Significance
FS         0010  0010   Field Separator
           0010  0011
BYP        0010  0100   Bypass
LF         0010  0101   Line Feed
ETB        0010  0110   End of Transmission Block

** Page 139

EBCDIC     bits         Notes
ESC        0010  0111   Escape
           0010  1000
           0010  1001
SM         0010  1010   Set Mode
CU2        0010  1011   Customer Use 1
           0010  1100
ENQ        0010  1101   Enquiry
ACK        0010  1110   Acknowledge
BEL        0010  1111   Bell
           0011  0000
           0011  0001
SYN        0011  0010   Synchronous Idle
           0011  0011
PN         0011  0100   Punch On
RS         0011  0101   Reader Stop
UC         0011  0110   Upper Case
EOT        0011  0111   End of Transmission
           0011  1000
           0011  1001
           0011  1010
CU3        0011  1011   Customer Use 3
DC4        0011  1100   Device Control 4
NAK        0011  1101   Negative Acknowledge
           0011  1110
SUB        0011  1111   Substitute
SP         0100  0000   Space

** Page 140


Modems and Services

The table below shows all but two of the types of service you are likely to
come across; V-designators are the world-wide 'official names given by the
CCITT; Bell-designators are the US names:

Service        Speed  Duplex  Transmit    Receive     Answer
Designator                    0    1      0     1

V21 orig       300(*) full    1180  980   1850  1650   -
V21 ans        300(*) full    1850 1650   1180   980  2100
V23 (1)        600    half    1700 1300   1700  1300  2100
V23 (2)       1200    f/h(**) 2100 1300   2100  1300  2100
V23 back        75    f/h(**)  450  390    450   390   -
Bell 103 orig  300(*) full    1070 1270   2025  2225   -
Bell 103 ans   300(*) full    2025 2225   1070  1270  2225
Bell 202      1200    half    2200 1200   2200  1200  2025

(*)any speed up to 300 baud, can also include 75 and 110 baud

(**)service can either be half-duplex at 1200 baud or asymmetrical
full duplex, with 75 baud originate and 1200 baud receive (commonly
used as viewdata user) or 1200 transmit and 75 receive (viewdata

The two exceptions are:
V22       1200 baud full duplex, two wire
Bell 212A The US equivalent
Both these services operate by detecting phase as well as tone.

British Telecom markets the UK services under the name of Datel as
follows--for simplicity The list covers only those services which use
the PTSN or are otherwise easily accessible--4-wire services, for
example are excluded.

** Page 141

Datel    Speed       Mode      Remarks

100(H)   50          async     Teleprinters, Baudot code
100(J)   75-110      async     News services etc, Baudot code
         50          async     Telex service, Baudot code
200      300         async     full duplex, ASCII
400      600 Hz      async     out-station to in-station only
600      1200        async     several versions exist--for 1200
                               half-duplex; 75/1200 for viewdata
                               users; 1200/75forviewdata hosts; and
                               a rare 600 variant. The 75 speed is
                               technically only for supervision but
                               gives asymetrical duplex

BT has supplied the following modems for the various services-- the
older ones are now available on the 'second-user' market:

Modem No Remarks

         1200 half-duplex--massive
 2       300 full-duplex--massive
11       4800 synchronous--older type
12       2400/1200 synchronous
13       300 full-duplex--plinth type
20(1)    1200 half-duplex--'shoe-box' style
  (2)    1200/75 asymetrical duplex--'shoe-box' style
  (3)    75/1200 asymetrical duplex--'shoe-box' style
21       300 full-duplex--modern type
22       1200 half-duplex--modern type
24       4800 synchronous--modern type (made by Racal)
27A      1200 full duplex, sync or async (US made &
         modified from Bell 212A to CCITT tones)
27B      1200 full duplex, sync or async (UK made)

   You should note that some commercial 1200/1200 full duplex modems
also contain firmware providing ARQ error correction protocols;
modems on both ends of the line must have the facilities, of course.

** Page 142

BT Line Connectors

   Modems can be connected directly to the BT network ('hard- wired')
simply by identifying the pair that comes into the building. Normally
the pair you want are the two outer wires in a standard 4 x 2 BT
junction box. (The other wires are the 'return' or to support a
'ringing' circuit.)

   A variety of plugs and sockets have been used by BT. Until
recently, the standard connector for a modem was a 4-ring jack, type
505, to go into a socket 95A. Prestel equipment was terminated into a
similar jack, this time with 5 rings, which went into a socket type
96A. However, now all phones, modems, viewdata sets etc, are
terminated in the identical modular jack, type 600. The corresponding
sockets need special tools to insert the line cable into the
appropriate receptacles.

   Whatever other inter-connections you see behind a socket, the two
wires of the twisted pair are the ones found in the centres of the
two banks of receptacles.  North America also now uses a modular jack
and socket system, but not one which is physically compatible with UK
designs...did you expect otherwise?

** Page 143


The Radio Spectrum

   The table gives the allocation of the radio frequency spectrum up
30 MHz. The bands in which radio-teletype and radio-data traffic are
most common are those allocated to 'fixed' services, but data traffic
is also found in the amateur and maritime bands.


  9       --      14     Radionavigation
 14       --      19.95  Fixed/Maritime mobile
 20                      Standard Frequency & Time
 20.05    --      70     Fixed & Maritime mobile
 70       --      90     Fixed/Maritime mobile/Radionavigation
 90       --     110     Radionavigation

 110      --     130     Fixed/Maritime mobile/Radionavigation
 130      --     148.5   Maritime mobile/Fixed
 148.5    --     255     Broadcasting
 255      --     283.5   Broadcasting/Radionavigation(aero)
 283.5    --     315     Maritime/Aeronautical navigation

 315      --     325     Aeronautical radionavigation/Maritime
 325      --     405     Aeronautical radionavigation
 405      --     415     Radionavigation (410 = DF)
 415      --     495     Aeronautical radionavigation/Maritime mobile
 495      --     505     Mobile (distress & calling) > 500:cw&rtty

 505      --     526.5   Maritime mobile/Aeronautical navigation
 526.5    --    1606.5   Broadcasting
1606.5    --    1625     Maritime mobile/Fixed/Land mobile
1625      --    1635     Radiolocation
1635      --    1800     Maritime mobile/Fixed/Land mobile
1800      --    1810     Radiolocation
1810      --    1850     Amateur
1850      --    2000     Fixed/Mobile

** Page 144

2000      --    2045     Fixed/Mobile
2045      --    2160     Maritime mobile/Fixed/Land mobile
2160      --    2170     Radiolocation
2170      --    2173.5   Maritime mobile
2173.5    --    2190.5   Mobile (distress & calling) >2182--voice
2190.5    --    2194     Maritime & Mobile
2194      --    2300     Fixed & Mobile
2300      --    2498     Fixed/Mobile/Broadcasting
2498      --    2502     Standard Frequency & Time
2502      --    2650     Maritime mobile/Maritime radionavigation
2650      --    2850     Fixed/Mobile
2850      --    3025     Aeronautical mobile (R)
3025      --    3155     Aeronautical mobile (OR)
3155      --    3200     Fixed/Mobile/Low power hearing aids
3200      --    3230     Fixed/Mobile/Broadcasting
3230      --    3400     Fixed/Mobile/Broadcasting
3400      --    3500     Aeronautical mobile (R)
3500      --    3800     Amateur/Fixed/Mobile
3800      --    3900     Fixed/Aeronautical mobile (OR)
3900      --    3930     Aeronautical mobile (OR)
3930      --    4000     Fixed/Broadcasting

4000      --    4063     Fixed/Maritime mobile
4063      --    4438     Maritime mobile
4438      --    4650     Fixed/Mobile
4650      --    4700     Aeronautical mobile (R)
4700      --    4750     Aeronautical mobile (OR)

4750      --    4850     Fixed/Aeronautical mobile (OR)/
                         Land mobile/Broadcasting
4850      --    4995     Fixed/Land mobile/Broadcasting

4995      --    5005     Standard Frequency & Time
5005      --    5060     Fixed/Broadcasting
5060      --    5450     Fixed/Mobile
5450      --    5480     Fixed/Aeronautical mobile (OR)/Land mobile
5480      --    5680     Aeronautical mobile (R)
5680      --    5730     Aeronautical mobile (OR)
5730      --    5950     Fixed/Land mobile

5950      --    6200     Broadcasting
6200      --    6525     Maritime mobile
6525      --    6685     Aeronautical mobile (R)
6685      --    6765     Aeronautical mobile ~OR)
6765      --    6795     Fixed/lSM

7000      --    7100     Amateur
7100      --    7300     Broadcasting
7300      --    8100     Maritime mobile

** Page 145

8100      --    8195     Fixed/Maritime mobile
8195      --    8815     Maritime mobile

8815      --    8965     Aeronautical mobile (R)
8965      --    9040     Aeronautical mobile ~OR)
9040      --    9500     Fixed
9500      --    9900     Broadcasting
ggoo      --    9995     Fixed

9995      --   10005     Standard Frequency & Time
10005     --   10100     Aeronautical mobile (R)
10100     --   10150     Fixed/Amateur(sec)
10150     --   11175     Fixed
11175     --   11275     Aeronautical mobile (OR)
11275     --   11400     Aeronautical mobile (R)
11400     --   11650     Fixed

11650     --   12050     Broadcasting
2050      --   12230     Fixed
12230     --   13200     Maritime mobile

13200     --   13260     Aeronautical mobile (OR)
13260     --   13360     Aeronautical mobile (R)
13360     --   13410     Fixed/Radio Astronomy
13410     --   13600     Fixed
13600     --   13800     Broadcasting
13800     --   14000     Fixed

14000     --   14350     Amateur
14350     --   14990     Fixed

14990     --   15010     Standard Frequency & Time
15010     --   15100     Aeronautical mobile (OR)
15100     --   15600     Broadcasting
15600     --   16360     Fixed

16360     --   17410     Maritime mobile
17410     --   17550     Fixed
17550     --   17900     Broadcasting
17900     --   17970     Aeronautical mobile (R)
17970     --   18030     Aeronautical mobile (OR)

18030     --   18052     Fixed
18052     --   18068     Fixed/Space Research
18068     --   18168     Amateur
18168     --   18780     Fixed
18780     --   18900     Maritime mobile
18900     --   19680     Fixed

** Page 146

19680     --   19800     Maritime mobile
19800     --   19990     Fixed
19990     --   20010     Standard Frequency & Time
20010     --   21000     Fixed
21000     --   21450     Amateur
21450     --   21850     Broadcasting
21850     --   21870     Fixed
21870     --   21924     Aeronautical fixed
21924     --   22000     Aeronautical (R)
22000     --   22855     Maritime mobile
22855     --   23200     Fixed
23200     --   23350     Aeronautical fixed & mobile (R)
23350     --   24000     Fixed/Mobile
24000     --   24890     Fixed/Land mobile
24890     --   24990     Amateur
24990     --   25010     Standard Frequency & Time
25010     --   25070     Fixed/Mobile
25070     --   25210     Maritime mobile
25210     --   25550     Fixed/Mobile
25550     --   25670     Radio Astronomy
25670     --   26100     Broadcasting
26100     --   26175     Maritime mobile
26175     --   27500     Fixed/Mobile (CB) (26.975-27.2835 ISM)
27500     --   28000     Meteorological aids/Fixed/Mobile (CB)
28000     --   29700     Amateur
29700     --   30005     Fixed/Mobile

Note: These allocations are as they apply in Europe, slight variations occur
in other regions of the globe.

** Page 147


Port-finder Flowchart

   This flow-chart will enable owners of auto-diallers to carry out
an automatic search of a range of telephone numbers to determine
which of them have modems hanging off the back.

   It's a flow-chart and not a program listing, because the whole
exercise is very hardware dependent: you will have to determine what
sort of instructions your auto-modem will accept, and in what form;
you must also see what sort of signals it can send back to your
computer so that your program can 'read' them.

   You will also need to devise some ways of sensing the phone line,
whether it has been seized, whether you are getting 'ringing', if
there is an engaged tone, a voice, a number obtainable tone, or a
modem whistle. Line seizure detect, if not already available on your
modem, is simply a question of reading the phone line voltage; the
other conditions can be detected with simple tone decoder modules
based on the 567 chip.

   The lines from these detectors should then be brought to a A/D
board which your computer software can scan and read.

** End of File
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