A ‘Trojan Horse’ application called Oompa-Loompa (OSX/Oomp-A or OSX/Leap-A) is making the rounds in the Macintosh universe. While this application is not a virus, it does have some virus- or worm-like properties and is probably the closest thing to affect the Mac platform since the launch of the Unix-based Mac OS X.
As in the past, some media outlets and companies will probably attempt to arouse concern of a major security threat against the Mac platform. But the Oompa-Loompa trojan can only activate when a user unpacks a tgz compressed file and double-clicks the application (which appears at a cursory glance to be an image file). The trojan then infects random applications and attempts to propagate via iChat (Apple’s AIM program), but the receiving users again can only be infected if they intentionally decompress and run the application.
In other words, don’t double-click strange files. This goes for users of all computer platforms. For more information on this trojan,is the best source.