TUCoPS :: General Information :: handbook.txt

The Hacker's handbook

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

1 First Principles                                                              5

2 Computer-to-computer communications                             10

3 Hackers' Equipment                                             17

4 Targets: What you can find on mainframes                       32

5 Hackers' Intelligence                                          44

6 Hackers' Techniques                                            66

7 Networks                                                       77

8 Viewdata systems                                              94

9 Radio computer data                                           106

10 Hacking: the future                                          115


I troubleshooting                                               119

II Glossary                                                     124

III CCITT and related standards                                 136

IV Standard computer alphabets                                  137

V Modems                                                        144

VI Radio Spectrum                                               146
VII Port-finder flow chart                                      150


	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

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

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.

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 thanks.

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.

	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

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

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 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 


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

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.


Computer-to-Computer Communications

	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 


	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.

(   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 working.

(   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'.
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'.

	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:





                     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.
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


	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.

	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.


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.

	hat 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


	ou 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.

	lthough 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 Cmputer

	lmost 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.

	(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.)

	ost 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'.

	ne 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.

	n alternative storage method is to save to a printer, printing

the received data stream not only to the computer screen, but also on
 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


	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.

	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)

	ou 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.

	epending 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.

	n 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


	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.

	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.

	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.

	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.

	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.

	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.

	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


	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.

	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 (view data host)

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.

	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 line.

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.

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.



	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.

	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


	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

	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.

	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.

	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


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.

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


	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.

	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.

	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.

	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


	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.


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.

	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

	ince 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.

	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)









Msg#: 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....

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.

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 comes.
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    :

:                           :

:                           :

:                           :


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.

	With 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

test...', then when you hang-up the phone rings. Pick it up and you

either get dial tone which indicates OK or you will get a recording

i.e 'poor insulation B line' telling you what's wrong. If you get

dial tone you can immediately dial 1305 to do a further test which

might say 'faulty dial pulses'.  Other numbers to try are 182, 184 or

185.  I have discovered my exchange (Pontybodkin) gives a test ring

for 1267.  These numbers all depend on you local exchange so It pays

to experiment, try numbers starting with 1 as these are all local

functions. Then when you discover something of interest let me know 

on this SIG.
Msg: 2241 *EREWHON*

12/04/83 20:48:49 (Read 65 Times)




There is a company (?) in the USA called Loopmaniacs Unlimited,

PO Box 1197, Port Townsend. WA, 98368, who publish a line of books on

telephone hacking.  Some have circuits even. Write to M. Hoy there.

One of their publications is "Steal This Book" at S5.95 plus about $4
post. Its Worth stealing, but don't show it to the customs!

Msg#: 3266 *EREWHON*

01/22/84 06:25:01 (Read 53 Times)

From: xxxxxxxxxx



As already described getting onto the UCL PAD allows various calls.

Via this network you can access many many university/research

computers To get a full list use CALL 40 then HELP, select GUIDE.

Typing '32' at the VIEW prompt will start listing the addresses. Host

of these can be used at the pad by 'CALL addr' where addr is the
address. For passwords you try DEMO HELP etc. If you find anything

interesting report it here.

HINT: To aviod the PAD hanging up at the end of each call use the

LOGON command - use anything for name and pwd. This seems to do the


Another number: Tel: (0235) 834531. This is another data

exchange. This one's a bit harder to wake up. You must send a 'break

level' to start. This can be done using software but with a maplin

just momentarily pull out the RS232 com. Then send RETURNs. To get a

list of 'classes' you could use say Manchesters HELP:- CALL 1020300,
user:DEMO pwd:DEMO en when you're on HELP PACX.

Msg#: 3687 *HACKER'S CLUB*

02/05/84 14:41:43 (Read 416 Times)

From: xxxxxxxxxxxx



The following are some of the numbers collected in the Hackers SIG:

Commodore BBS (Finland)       358 61 116223

Gateway test                  01 600 1261

PRESTEST (1200/75)            01 583 9412

Some useful PRESTEL nodes - 640..Res.D (Martlesham's experiments in

Dynamic Prestel DRCS, CEPT standards, Picture Prestel, 601

(Mailbox,Telemessaging, Telex Link - and maybe Telecom Gold), 651

(Scratchpad -always changing). Occasionally parts of 650 (IP News)

are not properly CUGed off. 190 sometimes is interesting well.

These boards all specialised in lonely hearts services !

The boards with an asterisk all use BELL Tones

*Fairbanks, AK,    907-479-0315

*Burbank, CA,      213-840-8252

*Burbank, CA,      213-842-9452
*Clovis, CA,       209-298-1328

*Glendale, CA,     213-242-l882

*La Palma, CA,     714-220-0239

*Hollywood, CA,    213-764-8000

*San Francisco CA, 415-467-2588

*Santa Monica CA,  213-390-3239

*Sherman Oaks CA,  213-990-6830

*Tar~ana , CA,     213-345-1047

*Crystal Rivers FL,904-795-8850

*Atlanta, GA,      912-233-0863

*Hammond, IN,      219-845-4200

*Cleveland, OH,    216-932-9845

*Lynnefield, MA,   6l7-334-6369

*Omaha, NE,        402-571-8942

*Freehold, NJ,     201-462-0435

*New York, NY,     212-541-5975

*Cary, NC,         919-362-0676

*Newport News,VA   804-838-3973

*Vancouver, WA,    200-250-6624

Marseilles, France 33-91-91-0060

Both USA nos. prefix (0101)

a) Daily X-rated Doke Service 516-922-9463

b) Auto-Biographies of young ladies who normally work in

unpublishable magazines on 212-976-2727.

c)Dial a wank 0101,212,976,2626; 0101,212,976,2727

Msg#: 3688 *HACKER'S CLUB*

02/05/84 14:44:51 (Read 393 Times)

From: xxxxxxxxxxx


Hertford PDP 11/70 Hackers BBS:

Call 0707-263577 with 110 baud selected.

type: SET SPEED 300'CR'

After hitting CR switch to 300 baud.

Then type: HELLO 124,4'CR

!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






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  

	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!

	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.

	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....

	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.

	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


	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.


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.

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 again:





	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


	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.

	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. 

	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.

	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.

	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


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.

	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.

	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).

	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....



	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.

	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
	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.

	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

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.




                                           |            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 networks using packet switching seek to be

compatible with each other, at least to a considerable degree. The

international standard they have to implement is called CCITT X.25.

This is a multi-layered protocol covering (potentially) everything

from electrical connections to the user interface.

The levels work like this:

7 APPLICATION User interface

6 PRESENTATION Data formatting & code conversion

5 SESSION Co-ordination between processes

4 TRANSPORT Control of quality service

3 NETWORK Set up and maintenance of connections

2 DATA LINK Reliable transfer between terminal and network

PHYSICAL Transfer of bitstream between terminal and network

	At the moment international agreement has only been reached on the

lowest three levels, Physical, Data Link and Network. Above that,

there is a battle in progress between IBM, which has solutions to the

problems under the name SNA (Systems Network Architecture) and most

of the remainder of the principal main- frame manufacturers, whose

solution is called OSI (Open Systems Interconnection).

Packet Switching and the Single User

	So much for the background explanation.  How does this affect the

user?  Single users can access packet switching in one of two

principal ways. They can use special terminals able to create the

data packets in an appropriate form--called Packet Terminals, in the

(In the original book there is a diagram showing Dial-up termials and

single users connecting to a PAD system and Packet Terminals directly

connected to the PSS. Note added by Electronic Images)

jargon--and these sit on the packet switch circuit, accessing it via

the nearest PSS exchange using a permanent dataline and modems

operating at speeds of 2400, 4800, 9600 or 48K baud, depending on

level of traffic. Alternatively, the customer can use an ordinary

asynchronous terminal without packet-creating capabilities, and

connect into a special PSS facility which handles the packet assembly
for him. Such devices are called Packet Assembler/ Disassemblers, or

PADs. In the jargon, such users are said to have Character Terminals.

PADs are accessed either via leased line at 300 or 1200, or via

dial-up at those speeds, but also at 110 and 1200/75.

	Most readers of this book, if they have used packet switching at

all, will have done so using their own computers as character

terminals and by dialling into a PAD. The phone numbers of UK PADs

can be found in the PSS directory, published by Telecom National

Networks.  In order to use PSS, you as an individual need a Network

User Identity (NUI), which is registered at your local Packet Switch

Exchange (PSE). The PAD at the PSE will throw you off if you don't

give it a recognisable NUI. PADs are extremely flexible devices; they

will configure their ports to suit your equipment, both as to speed

and screen addressing, rather like a bulletin board (though to be

accurate, it is the bulletin board which mimics the PAD).

Phone numbers to access PSS PADs

                           Terminal operating speed:

PSE              (STD)     110 OR 300  1200/75      1200 Duplex

Aberdeen         (0224)    642242      642484       642644

Birmingham       (021)     2145139     2146191      241 3061
Bristol          (0272)    216411      216511       216611

Cambridge        (0223)    82511       82411        82111

Edinburgh        (031)     337 9141    337 9121     337 9393

Glasgow          (041)     204 2011    204 2031     204 2051

Leeds            (0532)    470711      470611       470811

Liverpool        (051)     211 0000    212 5127     213 6327

London           (01)      825 9421    407 8344     928 2333

   or            (01)      928 9111    928 3399     928 1737

Luton            (0582)    8181        8191         8101

Manchester       (061)     833 0242    833 0091     833 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 code access to Slough is not available.

Switch the modem/dataphone to 'data' on receipt of data tone.

	Next, you need the Network User Address (NUA) of the host you are

calling.  These are also available from the same directory: Cambridge

University Computing Services's NUA is 234 222339399, BLAISE is 234

219200222, Istel is 234 252724241, and so on. The first four numbers
are known as the DNIC (Data Network Identification Code); of these

the first three are the country ('234' is the UK identifier), and the

last one the specific service in that country, '2' signifying PSS.

You can also get into Prestel via PSS, though for UK purposes it is

an academic exercise: A9 234 1100 2018 gives you Prestel without the

graphics (A9 indicates to the system that you have a teletype


	Once you have been routed to the host computer of your choice,

then it is exactly if you were entering by direct dial; your password

and so on will be requested.  Costs of using PSS are governed by the

number of packets exchanged, rather than the distance between two

computers or the actual time of the call. A typical PSS session will

thus contain the following running costs: local phone call to PAD (on

regular phone bill, time-related), PSS charges (dependent on number

of packets sent) and host computer bills (which could be time-related

or be per record accessed or on fixed subscription).

	Packet switching techniques are not confined to public data

networks Prestel uses them for its own mini-network between the

various Retrieval Computers (the ones the public dial into) and the

Update and Mailbox Computers, and also to handle Gateway connections.

Most newer private networks are packet switched.
	Valued Added Networks (VANs) are basic telecoms networks or

facilities to which some additional service--data processing or

hosting of publishing ventures, for example--has been added.

	Public Packet Switching, by offering easier and cheaper access, is

a boon to the hacker. No longer does the hacker have to worry about

the protocols that the host computer normally expects to see from its

users. The X.25 protocol and the adaptability of the PAD mean that

the hacker with even lowest quality asynchronous comms can talk to

anything on the network. The tariff structure, favouring packets

exchanged and not distance, means that any computer anywhere in the

world can be a target.

	Austin and Poulsen, the ARPAnet hackers, made dramatic use of a

private packet-switched net; the Milwaukee 414s ran around GTE's

Telenet service, one of the biggest public systems in the US. Their

self-adopted name comes from the telephone area code for Milwaukee, a

city chiefly known hitherto as a centre of the American beer

industry. During the Spring and Summer of 1983, using publicly

published directories, and the usual guessing games about

pass-numbers and pass-words, the 414s dropped into the Security

Pacific Bank in Los Angeles, the Sloan-Kettering Cancer Clinic in New

York (it is still not clear to me if they actually altered patients
records or merely looked at them), a Canadian cement company and the

Los Alamos research laboratory in New Mexico, home of the atomic

bomb, and where work on nuclear weapons continues to this day. It is

believed that they saw there 'sensitive' but not 'classified' files.

	Commenting about their activities, one prominent computer security

consultant, Joesph Coates, said: 'The Milwaukee babies are great, the

kind of kids anyone would like their own to - ~be...There's nothing

wrong with those kids. The problem is with the idiots who sold the

system and the ignorant people who bought it. Nobody should buy a

computer without knowing how much ~ .  security is built in....You

have the timid dealing with the foolish.'

	During the first couple of months of 1984, British hackers carried

out a thorough exploration of SERCNET, the private packet-switched

network sponsored by the Science and Engineering Research Council and

centred on the Rutherford Appleton Laboratory in Cambridge. It links

together all the science and technology universities and polytechnics

in the United Kingdom and has gateways to PSS and CERN (European

Nuclear Research).

	Almost every type of mainframe and large mini-computer can be

discovered hanging on to the system, IBM 3032 and 370 at Rutherford

itself, Prime 400s, 550s and 750s all over the place, VAX 11/780s at
Oxford, Daresbury, other VAXs at Durham, Cambridge, York, East Anglia

and Newcastle, large numbers of GEC 4000 family members, and the odd

PDP11 running Unix.

	Penetration was first achieved when a telephone number appeared on

a popular hobbyist bulletin board, together with the suggestion that

the instruction 'CALL 40' might give results. It was soon discovered

that if the hacker typed DEMO when asked for name and establishment,

things started to happen. For several days hackers left each other

messages on the hobbyist bulletin board, reporting progress, or the

lack of it. Eventually, it became obvious that DEMO was supposed, as

its name suggests, to be a limited facilities demonstration for

casual users, but that it had been insecurely set up.

	I can remember the night I pulled down the system manual, which

had been left in an electronic file, watching page after page scroll

down my VDU at 300 baud. All I had had to do was type the word

'GUIDE'. I remember also fetching down lists of addresses and

mnemonics of SERCNET members. Included in the manual were extensive

descriptions of the network protocols and their relation to

'standard' PSS-style networks.

	As I complete this chapter I know that certain forms of access to

SERCNET have been shut off, but that hacker exploration appears to
continue. Some of the best hacker stories do not have a definite

ending. I offer some brief extracts from captured SERCNET sessions.

03EOEHaae NODE 3.

Which Service?




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:


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


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 to

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:

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:


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.

	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 '@')

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:



	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


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.

	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:




      ---------------------+----------------------- ...

      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




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?

(   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....

	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.

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.

	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


                    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.

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.

	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.

	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.

	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?


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.

	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

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.

	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 is)

	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


	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):

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).

	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.

	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.






































































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.

	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 pportunities for 

the hacker. The technology we can afford has suddenly become much more 


	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,


	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.

	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?


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.

(   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 garbled

(   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.

(   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.

(   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.

You wish to get into the operating system from an applications program.

(   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.



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.

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.


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.


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



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.


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.


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.

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 number.

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.


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.

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.


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.


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.


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.


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 circuits

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


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

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 transmit

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

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

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.


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.

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

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.

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

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


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.

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.

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?


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 radiobeacons

 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

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

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

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.


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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