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APPROACHING ZERO

A Prestel subscriber dialled into the service via a normal phone line connected to his PC by a modem – the sophisticated device that allows physically separate computers to send tones over phone lines. At the Prestel end, another modem turned those tones back into commands to the system's own computer. The user, in essence, manipulated Prestel's computer from his PC.

Like all public-access computer systems, Prestel required users to key in their ID (sometimes called a log-in or a username) and their password. These are personal and known only to the individual subscribers. On Prestel, the ID was a ten character string of letters and numbers; the password was a four character string. Prestel also provided subscribers with their own 'electronic mailboxes', or MBXs, in which messages from other subscribers can be received. The system also includes an index of all subscribers and their MBX addresses, so users can communicate with each other.

Triludan's penetration of the Prestel system was a lucky fluke. In February 1984 he had dialled up Prestel from his home computer at 2.30 a.m. For no obvious reason, he entered ten 2s. To his surprise, a message came back saying 'correct'. He assumed that if the ID was that simple, then the four character password must be equally obvious. He tried '1234', and 'Welcome to the Prestel test' came up on the screen. 'So this is hacking,' he thought to himself.

The service Triludan had accessed was only the test system, set up for Prestel engineers to verify that their computers were operating correctly. Prestel subscribers dialled into any one of ten mainframes scattered around the country; the test system was confined to four other computers that simply monitored the mainframes. Because it was isolated from the actual Prestel service, it afforded few opportunities for exploration. None the less, Triludan continued to access the test system once a week to see if he could make any progress. One day in October 1984 he dialled up as usual and found an ID and password on the front page, just below the 'Welcome to the Prestel test' message. He then redialled the test service and entered the new ID. It turned out to be that of the system manager.

Hacking, Triludan decided, was stumbling across other people's mistakes.

The ID and password had been listed on the front page for the

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