A variant of a popular Windows-based Trojan targeting Mac OS X has surfaced, demonstrating that Macs and Windows are quite vulnerable to the same kind of threats. According to the security firm Sophos, the Trojan is a variant of a Windows-based remote access Trojan (RAT) called darkComet.

The company has labeled the malware OSX/MusMinim-A, or MusMinim for short, while the Trojan, however, refers to itself as "BlackHole RAT." Sophos says the Trojan is very basic, and can be wiped out with up-to-date antivirus software. Nevertheless, it acts as a necessary reminder that no system is immune to malicious threats.

As Apple's platform grows increasingly popular, its "security through obscurity" defense becomes less certain. Among the Trojan's tricks, it opens a full-screen window from which a user has only one choice—to click a Reboot button. The window contains a text message whose opening words invoke Apple's popular "I'm a Mac" ad campaign: "I am a Trojan Horse, so I have infected your Mac Computer."

According to Sophos, the Trojan, still a work in progress, has other disruptive activities; placing text files on the desktop, running arbitrary shell commands, and issuing restart, shutdown, and sleep commands.