IM worm

( -em w rm) (n.) A worm (i.e., a self-replicating program typically designed to perform harm to a computer or network) that propagates over instant messaging applications. The worm spreads by accessing the user’s instant messaging address book, or buddy list, and sends itself to individual recipients from that list.

Like a worm that spreads over the Internet, an IM worm can crash a system or allow a malicious hacker to gain access to a user’s device. Unlike the traditional form of a worm, an IM worm does not have to scan the Internet looking for vulnerbale IP addresses as it spreads by taking names from user address books and identifying who is currently online and therefore vulnerable.