W is for Worm. Among boring people, this means write-once, read- many. But among those who like a bit of spice in their computing lives, it evokes memories of 1988, and particularly Robert Morris, son of a US National Security Agency executive and a graduate student in computer science at Cornell University. He wrote a program that took advantage of holes in the Unix sendmail program. He reckoned his worm would spread slowly, copying itself with email and finger requests. It had no "purpose" except to copy itself.

He decided to test it by releasing it into the wild - the Internet. The program ran amok: it had a bug which meant it replicated far faster than Morris had expected. Many machines crashed, at sites including universities, military organisations, and medical research facilities. The estimated cost of dealing with the worm ranged from $200 to more than $53,000.

Programmers worked non-stop to get a temporary fix to slow down the worm's spread. A team at Berkeley University found a solution after about 12 hours; another was worked out at Purdue University. Many sites disconnected from the network, hampering the distribution of solutions.

Morris was later named in the New York Times as the author and subsequently convicted of violating the Computer Fraud and Abuse Act (Title 18), and sentenced to three years of probation, 400 hours of community service, a fine of $10,050, and costs of his supervision. His appeal was rejected.