Gatekeeper is a security feature of the macOS operating system by Apple. It enforces code signing and verifies downloaded applications before allowing them to run, thereby reducing the likelihood of inadvertently executing malware. Gatekeeper builds upon File Quarantine, which was introduced in Mac OS X Leopard and expanded in Mac OS X Snow Leopard. The feature originated in version 10.7.3 of Mac OS X Lion as the command-line utility spctl. A graphical user interface was originally added in OS X Mountain Lion (10.8) but was backported to Lion with the 10.7.5 update.