Can't be 100% sure but Mackeeper is the likely reason. Read the links below and get rid of it as soon as possible.
And for more advice on this subject.
Malware. Thomas' Corner : Mac Malware Guide and ...
..., recently I purchased MacKeeper, and seems that the problem occured when I start using it. ...
MacKeeper... most likely the source of your issues...
Read Here > Do not install MacKeeper
And Here > Beware MacKeeper
In General 3rd Party AV Software is Not Required as Mac OS X tends to look after itself.
See Here > Antivirus Discussion
The Safe Mac > http://www.thesafemac.com/mmg/