Some apps downloaded and installed from the Internet could adversely affect your Mac. Gatekeeper helps protect your Mac from such apps. Read this article to learn about Gatekeeper and its options. Gatekeeper is a new feature in Mountain Lion that builds on OS X's existing malware checks to help protect your Mac from malware and misbehaving apps downloaded from the Internet. The safest and most reliable place to download and install apps is via the Mac App Store. Apple reviews each app before it's accepted by the store, and if there's ever a problem with an app, Apple can quickly remove it from the store. For apps that are downloaded from places other than the Mac App Store, developers can get a unique Developer ID from Apple and use it to digitally sign their apps. The Developer ID allows Gatekeeper to block apps created by malware developers and verify that apps haven't been tampered with since they were signed. If an app was developed by an unknown developer