Gatekeeper is a new feature in Mac OS X Lion or later that builds on OS X’s existing malware checks to help protect your Mac from malware and other types of mischievous software downloaded from the Internet.
Your Apple Macintosh or Mac Book does not require anti-virus or so-called “cleaning apps” in fact they can slow down your Mac and in certain cases completely cripple your operating system.
I have been working with Macintosh computers going back to the very first Macintosh computers in 1984. I have also been directly in charge of more than 70 Macintosh computers in a very mission critical environment. Never once was there a virus found that infected one of those computers.
Cross-reference that today with more than a dozen of Mac computers that had a cleaning or anti-virus software installed where I have had to spend hours removing malware from those computers.
Save your money and possibly having your computer hacked by staying far away from anti-virus software, and Mac Defender type programs for Apple computers. If Apple intended the Macintosh operating system to use these programs they would come preinstalled on the computer just as Microsoft Windows preinstalls Malware software with their operating systems.
I hope that you do not have problems with your computer, but if you do, take your computer to an authorized Apple repair technician and have them diagnose the problems.