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Another possibility is to check in your Safari Preferences/extensions. I have seen that some of those spammed apps, like MacKeeper, now may add extensions, when you click on the "wrong" link - similar to some that add toolbars to IE when you use Windows.
 
Not sure if this is what you're looking for, but if you are using Safari, do you have "Block Pop Ups" enabled in preferences. Also, Adblock will help.

Another possibility is to check in your Safari Preferences/extensions. I have seen that some of those spammed apps, like MacKeeper, now may add extensions, when you click on the "wrong" link - similar to some that add toolbars to IE when you use Windows.

block pop ups is enabled, checked extensions as well, still getting the mac keeper pop up:(
 
You can look in the various "launch..." folders on your Mac.
Look for either Mackeeper, or Zeobit name in the /Library/LaunchDaemons, or /Library/LaunchAgents folders. There's the same folders in your ~/Library/ folder, too.
 
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