Worm

A program that replicates itself throughout a computer system. These copies can be made on the same computer or transferred to other machines via networks. The word was first used to describe a program that benignly duplicated itself around a network, utilising otherwise unused resources on networked workstations to conduct distributed computation. Some worms are security hazards because they use networks to spread themselves against the wishes of system administrators and disrupt networks by overloading them. A worm is similar to a virus in that it replicates itself, but it does not need to attach to specific files or sectors.