microsoft security alert = rootkits are here to come
rootkits are traditionally used by unix-linux system and they take over a system without anything or anyone seeing it at first. The windows environment wasn't know for this kind of stuff, but now it is here and here to stay, so they say.
One rootkit is Hacker defender
to be found here http://hxdef.czweb.org/ with anti-detection test
removal tool http://www.securiteam.com/tools/6J00L2ABFO.html