There appear to be two versions of MacKeeper floating around:
One is the legit version which is, according to the posts here, not effective and unnecessary, and
the other is a version of the trojan currently masquerading under several names.
In either case, I would not let it near my Mac. Here is the Apple info in case it is the trojan:
FWIW, there are no viruses for Mac. Do not trust such silly marketing tequniques. Do not download anything unless you know what it is. And, most of all, don't install anything unless you are 1000% sure of what it is.
If you (or someone using your computer) so much as clicks on an offer for MacKeeper, you are entering the gates of computer ****. "Lasciate ogne speranza, voi ch'intrate" or "Abandon all hope, ye who enter here."
After the offer was clicked on, (MacKeeper was never purchased or activated) my laptop (only 6 months old) began running slower and slower, and hotter and hotter. Safari started crashing and then Firefox was not responding. And then funny things began happening to my OS. Went to an Authorized Mac Service provider and *they* were not able to trash the program, because it infiltrates and imbeds itself in so many places. They called MacKeeper malware.
I've spent two days trying to find out how to remove it and get things back to a pre-MacKeeper state. Reinstalled my OS and all of the software updates and finally, after a search and destroy mission for anything with derivatives of com.zeobit.MacKeeper, I am back to a faster and cooler running computer.
Burn in Dante's Inferno forever MacKeeper!