From the JargonFile:
[from tapeworm in John Brunner's novel The Shockwave Rider, via XEROX PARC? A program that propagates itself over a network, reproducing itself as it goes. Compare Virus. Nowadays the term has negative connotations, as it is assumed that only crackers write worms. Perhaps the best-known example was Robert T. Morris's Great Worm of 1988, a ‘benign’ one that got out of control and hogged hundreds of Suns and VAXen across the U.S.
MyDoom and many other email-borne malware are viruses.
2 pages link to Worm:
