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Mac Defender (also known as Mac Protector, Mac Security, Mac Guard, Mac Shield, and FakeMacDef) is an internet rogue security program that targets computers running macOS. The Mac security firm Intego discovered the fake antivirus software on 2 May 2011, with a patch not being provided by Apple until 31 May. The software has been described as the first major malware threat to the Macintosh platform (although it does not attach to or damage any part of OS X). However, it is not the first Mac-specific Trojan, and is not self-propagating.
A variant of the program, known as Mac Guard, has been reported which does not require the user to enter a password to install the program, although one still does have to run the installer.

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