Worms (Family Safety)
A computer worm is a type of malicious software that will replicate itself and propogate to other computers on a network, usually without any user intervention. Unlike a computer virus, the user usually does not need to run any application to cause the worm to replicate itself. Not all worms are dangerous, but most anti-virus applications will detect and remove them.
For more information, see the computer worm entry in Wikipedia.