Apple has released Security Update 2011-003 for Mac OS X in response to the recent Mac fake anti-virus software.  This update:

• adds a malware definition to the File Quarantine application
• causes the File Quarantine application to automatically update its malware definition list daily
• removes MacDefender fake anti-virus software if detected

US-CERT encourages users and administrators to review Apple article HT4657 and apply Security Update 2011-003 to mitigate the risks.

Read more: US-CERT Current Activity