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exhibit 'fraud and deceit'. The sentence was three years' probation, a fine of $10,000 and 400 hours' community service.

The program that Morris released on to ARPANET was a worm. A worm has been defined as a program that takes up residence in a computer's memory, rather in the way a real worm takes up residence in an apple. Like the biological worm, the electronic worm reproduces itself; unlike the real-life worm, though, the spawn of the computer worm will live in another machine, and generally remain in communication with its progenitor. Its function is to use up space on the computer system and cause the machine to slow down or crash.

To researchers, there is a clear distinction between worms and viruses - which are separate sorts of malicious programs that require a host, a program or file on a disk or diskette they can attach themselves to. Viruses almost always have a payload as well, which is designed to change or modify or even attack the system they take residence on.

The fact that worms can move from one linked machine to another has always intrigued programmers, and there have been a number of attempts to harness this ability for beneficial purposes. One of the first experiments was made, ironically, on ARPANET. A demonstration program called Creeper was designed to find and print a file on one computer, then move to a second and repeat the task. A later version not only moved through computers performing chores, but could also reproduce, creating perfect clones of itself which would undertake the same chores and replicate again. The problem became obvious: the number of worms would increase exponentially as each generation of clones would replicate, creating more clones which would replicate, and so on.

The solution was to create another, non-replicating worm, called the Reaper, which would crawl through the system behind the Creeper and kill off the proliferating number of clones after they had performed their tasks. The experiment was abandoned when it became apparent that the reaper would never be able to keep up with the proliferating number of creepers.

There are other sorts of malicious programs, including what are known as 'trojans' - after the Greek wooden horse. The first major

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