CWmike writes: Apple released an update for Snow Leopard on Tuesday that warns users that they've downloaded fake Mac security software and scrubs already-infected machines. Chet Wisniewski, a security researcher with Sophos, confirmed that the update alerts users when they try to download any of the bogus MacDefender antivirus software. Wisniewski had not yet tested the malware cleaning functionality of the update, but was confident that it would work. 'It's reasonably trivial to remove MacDefender,' said Wisniewski. 'It's not burying itself in the system, not compared to some of some of the crap that we see on Windows.' The update, labeled 2011-003, adds a new definition to the rudimentary antivirus detection engine embedded in Mac OS X 10.6, aka Snow Leopard, and also increases the frequency with which the operating system checks for new definitions to daily.