updated 01:40 pm EDT, Wed October 19, 2011
Could open affected Macs to other attacks
A Mac Trojan now in circulation attempts to disable OS X's built-in anti-malware protection, known as XProtect, according to security firm F-Secure. Identified with the label OSX/Flashback.C, the Trojan first decrypts the paths of XProtectUpdater files, then unloads the XProtectUpdater daemon. To finish the job, the malware then overwrites the XProtectUpdater files with a blank character.
Without XProtectUpdater in action, OS X can no longer fetch further updates to its list of definitions, making it possible for subsequent attacks to go unchallenged. F-Secure remarks that it's common for malware to try to disable a computer's defenses. Flashback.C, though, may be the first Mac-oriented malware to intentionally try crippling XProtect. The technology is built into OS X Lion, as well as recent versions of Snow Leopard.