IM worm

An IM worm is self-replicating malicious code that spreads in instant messaging networks. When an IM worm infects a computer, it locates the address book for the instant messenger client, which is called a buddy list or contact list, and tries to send itself to all the infected person's contacts. Some IM worms rely on social engineering techniques to trick the recipient into accepting a message that contains the malicious code. Choke, CoolNow, and NewPic are three well-known IM worms.