Apple has released the Security Update 2011-003 in order to protect Mac users from the Mac Defender Trojan horse, as well as future malware.

Last week Apple published details of how to manually remove the Mac Defender Trojan horse, as well as promising to roll out a security update that would deal with the malware.

The Security Update 2011-003 requires Mac OS X Snow Leopard 10.6.7 and it tackles Mac Defender.

Apple has updated the malware definitions contained in Snow Leopard's built-in File Quarantine malware protection, to identify the OSX.MacDefender.

Apple also added Snow Leopard's malware protection daily definition updates. The system will check daily for updates to the File Quarantine malware definition list. This gives Apple the ability to add new definitions in the background, without requiring users to manually download a Security Update.

And of course, Snow Leopard can now remove the Mac Defender Trojan horse if it's detected on your system. If a known variant was detected and removed, you will be notified via an alert after the update is installed.