It's usually fake alert. A fake AV program. It's a ***** to get rid of, but it's possible. There are several tools you can use, but be careful. They can be as bad as the malware. I actually work for one of the AV companies so I'm very familiar with this junk. Most big name AV vendors can't/don't keep up with this particular one since it morphs so quickly. Best thing to run is Firefox and the no-scripts add-on.