Researchers from F-Secure warn that a variant on a trojan discovered in September, which masquerades as an Adobe Flash Player installer, now exists and is capable of disabling OS X's built-in malware protection.
OSX/Flashback.C disables the auto-updater component of XProtect, which means the system's built-in anti-malware application no longer looks for updates to its malware definitions. This essentially holds the door open for future malware to invade the system unimpeded.
F-Secure provides instructions for removing OSX/Flashback.C if you
