OSX/Tsunami-A, a new Trojan horse for Mac OS X has been discovered by Sophos. The Trogan is a port of the linux virus, Troj/Kaiten. Which embeds itself into the system and listens for commands on an IRC network. What makes this Trojan particularly nasty is that the controller can instruct your computer to DDoS (distributed denial-of-service) a particular computer/server/ip address. The trojan also allows the controller to run any script or command on your Mac as they wish.
Participating in a DDoS is illegal, so make sure your protected now. Sophos’ OS X applications have been updated to detect and remove OSX/Tsunami-A. Not protected? Download Sophos for free.
Source: Naked Security