'''Mac Defender''' (noto anche come '''Mac Protector''', '''Mac Security'''<ref name=how-to-avoid>{{cite web|title=HowCome toevitare avoido orrimuovere removeil malware Mac Defender malware|url=http://support.apple.com/kb/HT4650?viewlocale=it_IT|work=Apple Support|accessdate=2629 May 2011|date=2011-05-2425}}</ref> e '''Mac Guard'''<ref>Intego ''Mac Security Blog'' 25 May 2001, http://blog.intego.com/2011/05/25/intego-security-memo-new-mac-defender-variant-macguard-doesnt-require-password-for-installation/</ref>) è un [[malware]] mascherato da un programma [[antivirus]] che gira su computer con [[Mac OS X]]. Le prime "indiscrezioni" di tale software emersi nel maggio 2011<ref name=wisniewski>{{cite web|last=Wisniewski|first=Chester|title=Mac users hit with fake anti-virus when using Google image search|url=http://nakedsecurity.sophos.com/2011/05/02/mac-users-hit-with-fake-av-when-using-google-image-search/|work=Naked Security|publisher=Sophos|accessdate=24 May 2011|date=2011-05-02}}</ref>. Il software è stato descritto come la prima minaccia assoluta [[malware]] per la piattaforma [[Macintosh]]<ref>"Macs face first virus threat" 4th May, 2011, http://www.techday.co.nz/netguide/news/macs-face-first-virus-threat/20020/ </ref><ref>"Say hello to MAC Defender, the first major widespread piece of Mac based malware." http://www.left-click.us/news/blog/mac-defender</ref><ref>"Mac Defender has been making a lot of noise as one of the first major Mac security threats" Adam Dachis, 25 May, 2011, "How to Protect Your Computer from Mac Defender and Its Counterparts" http://lifehacker.com/5805609/how-to-protect-your-computer-from-mac-defender-and-macguard</ref><ref>"By and large, Mac users have been able to escape the onslaught of malware that their Windows counterparts suffer from." May 2, 2011 2:34 pm by Dan Moren "New Mac Trojan horse masquerades as virus scanner" http://www.macworld.com/article/159595/2011/05/macdefender_trojan_horse.html</ref><ref>"The old saw that Macs don't get viruses is under fire as a piece of malware called Mac Defender is rampaging across the Web." Rich Trenholm, 19 May 2011, ''Cnet.com'', "Mac Defender fake antivirus software is first major attack on Apple computers