01-14-2013, 12:31 AM
This sort of thing has been available, and probably done by default on most user's Macs since 10.6. A file called Xprotect.plist gets updated. It's been referred to as Xprotect for that reason but Apple doesn't call it that; some other company owns that name for something else. A company making software that let's you tweak that file (Xprotect Brain) describes like this:
With this security update, Apple added an option to the "General" tab of the "Security" System Preferences panel labeled "Automatically update safe downloads list". If this option is enabled (which it is by default) then approximately every 24 hours the system will check Apple's servers to see if a new version of the malware definition list is available, and will install the update if found.
If the option is turned off, then no automatic malware definition update will take place.