After the Mac Defender fake anti-virus malware surfaced then mutated, and the criticism levelled against it for telling help desk reps not to help remove the program, it seems Apple has stepped up to the plate with the latest OSX security update.
The newest security update includes quarantine and removal processes for the known variants of the Mac Defender malware.
Impact: Definition added
Description: The OSX.MacDefender.A definition has been added to the malware check within File Quarantine. Information on File Quarantine is available in this Knowledge Base article: http://support.apple.com/kb/HT3662
Impact: Automatically update the known malware definitions
Description: The system will check daily for updates to the File Quarantine malware definition list. An opt-out capability is provided via the "Automatically update safe downloads list" checkbox in Security Preferences. Additional information is available in this Knowledge Base article: http://support.apple.com/kb/HT4651
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