The anti-malware system built into recent releases of Mac OS X, known as XProtect but officially called File Quarantine, protects Macs from infection by certain malicious software. It made its debut in late 2009 in a beta version of Mac OS X Snow Leopard, blocking RSPlug and iServices, and later HellRTC, OSX.OpinionSpy and MacDefender. It is periodically updated to protect against new malware.