Stay away from MacKeeper! Purge your system, DO NOT INSTALL.
I made the mistake of trying it out once. It does not like being uninstalled. Took quite a bit of google searching to get rid of this malware. Had to go deep in my file system to delete obscure files. It literally didn't have an uninstaller when I tried it.
Plus having random ads and messages pop up isn't nice. In fact stay away from any software by Zeobit. If it's in ads everywhere, it's malware.
You Mac doesn't need any protection. It's default tools are good enough and there is freeware that can do other stuff like consolidate chunks of data and fix file permissions.
Possibly a side effect or might not be: When I installed MacKeeper and opened a webpage, every ad I ever saw was a MacKeeper ad. It made me suspicious that MacKeeper replaced page ads with it's own ads.
Also stay away from similar products that claim to fix your machine.
I don't know if the developers of MacKeeper are sleazy or just really bad. With all the problems MacKeeper causes it could be either intentional or unintentional malware. I do have one positive thing about it, it is a pretty program.
References:
https://discussions.apple.com/docs/DOC-3036https://discussions.apple.com/thread/4276731?start=0&tstart=0Edit:
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