worm

n. [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. See also
cracker , RTM , Trojan horse , ice.