Imaut.c is an Internet worm that spreads through instant messages using Yahoo! Messenger, Windows Live Messenger and AIM programs. The parasite’s messages contain links to malicious web pages. Once the user clicks on such a link, the worm gets secretly downloaded and installed to the system. Then it runs a spreading routine and a payload. Imaut.c changes the Internet Explorer default home page, disables the Task Manager and the Registry Editor and modifies certain Yahoo! Messenger settings. It is able to update itself via the Internet. The parasite runs on every Windows startup.