With developers needing to prepare for Apple's new Gatekeeper feature in OS X 10.8 Mountain Lion, Apple has revealed that the functionality is already baked into OS X 10.7.3 but hidden by default. Apple has instructed developers that they can enable Gatekeeper on OS X 10.7.3 from the command line in order to test the functionality.
Running the command "sudo spctl --enable" in Terminal will enable Gatekeeper on OS X 10.7.3, and the system can be turned off by replacing "enable" with "disable". With the system enabled, developers can then test how their applications will behave on systems using Gatekeeper.Mac OS X users will soon have the option of turning on Gatekeeper, a new Mac OS X security feature. When a user does this, the system provides an additional measure of safety: it blocks that user from opening newly-downloaded applications that are not Developer ID-signed. In this scenario, the same user is easily able to launch downloaded applications that are Developer ID-signed.
By default, Gatekeeper is not enabled in Mac OS X v10.7.3. For testing purposes, you can turn it on by using the new Mac OS X system policy control command-line tool, spctl(8).
Warning for non-signed application download with Gatekeeper activated on OS X 10.7.3
In another sign of Apple's desire to quickly implement Gatekeeper, Panic's Cabel Sasser notes that Apple contacted select developers last week to invite them to learn more about the feature.
Article Link: Gatekeeper Already Present in OS X 10.7.3, Available for Developer Testing