Fizzer, a mass mailing virus that allows control of the recipient's computer over IRC has annoyed IRC operators to the extent that they are creating a more-or-less permanent standby communication mechanism for fighting future threats.

The use of IRC by the software has drown some IRC channels and servers in many times more traffic than normal.

An article on CNET explains that the relatively fast-spreading virus gets its extra punch by spreading using both email and the Kazaa p2p file sharing network.

As usual, the virus only runs on Microsoft Windows, so you won't be able to be infected if you have a Macintosh.