Ten days ago, I published an article in this newsletter entitled Malware Found on Macintosh Systems. It described a newly-discovered Trojan Horse program called Mac Defender (there are other variants called Mac Protector and Mac Security). Luckily, it is a minor problem, easily avoided and, if installed, easily removed. You can read the article at http://goo.gl/7Xop3.
Now Apple has released a security update that neutralizes the problem. If Mac Defender or any similar software is encountered on a web site or in email, it will be blocked. If Mac Defender or its variants are already installed on the system, the new update will remove them. It also installs safeguards against similar future malware (malevolent software) programs.
Actually, Apple has always included malware prevention software in Snow Leopard although most Mac users were unaware of the protections because of the rarity of the problem(s). The new software update simply expands the anti-malware software that was already included in all Snow Leopard versions. The Mac Defender malware and its variants used a loophole in the Snow Leopard anti-malware software. The new Security Update closes that loophole.
Security Update 2011-003 includes changes to the File Quarantine feature and also includes definitions for Mac Defender and its known variants, as well as an automated removal tool. It works only with the most recent version of Snow Leopard, 10.6.7. Earlier versions of OS X are apparently not included.
The new malware protection will automatically be installed in all Snow Leopard systems on the next software update, if the user agrees. The user will be asked first before the updates are installed. You can read more in Apple's support note at http://support.apple.com/kb/HT4657.
You might also want to read earlier support notes about the same topic at http://support.apple.com/kb/HT4651 and at http://support.apple.com/kb/HT3662.
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