Fake MS Malicious Software Tool

While surfing the net this morning I received this pop-up window.  It looked just like it came from the windows update, lower right corner.  After a few seconds with out clicking on anything, a download window with an executable file poped up.  

 

However, I was using the Firefox browser and knew something was wrong.  I stopped all Internet activity with Zone Alarm firewall so I could investigate and kill it.  The avarage user would likeley have installed this thing.