Ghostbuster
From, Bruce Schneier's crypto gram, I found this is really cool research project from Microsoft. He blogged about it in Feb. I wonder if the spyware tool released by Microsoft, contains this.
From the blog:
It's a really elegant idea, based on a simple observation: the rootkit must exist on disk to be persistent, but must lie to programs running within the infected OS in order to hide.
If you want the dirty details,
http://www.usenix.org/events/lisa03/tech/wang/wang_html/index.html.