IM Worms spread via instant messaging systems (such as ICQ, MSN Messenger, AOL Instant Messenger, Yahoo Pager, Skype, etc.)

In order to spread, IM-Worms usually send a link (URL) to a list of message contacts. The link leads to a network resource where a file containing the body of the worm has been placed. This tactic is almost exactly the same as that used by Email-Worms.