As rumored, Apple has released a software update (“Security Update 2011-003“) to deal with the particularly notorious MacDefender malware. The update will add the OSX.MacDefender.A definition to the file quarantine list and scan the system to determine if the malware is present. MacDefender will be removed automatically on infected systems and users will be alerted and quarantine-enabled apps, such as Mail, Safari, and others, will automatically alert the user when a malicious program is downloaded. The latest version MacDefender does not need admin privileges to be installed, so make sure to update your system via Software Update as soon as possible.
Available for: Mac OS X v10.6.7, Mac OS X Server v10.6.7
Impact: Remove the MacDefender malware if detected
Description: The installation process for this update will search for and remove known variants of the MacDefender malware. If a known variant was detected and removed, the user will be notified via an alert after the update is installed. Additional information is available in this Knowledge Base article: http://support.apple.com/kb/HT4651