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 {cracker}s write worms. Perhaps the best-known example was Robert T. Morris's `Internet 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}, and {Great Worm, the}.