Someone also running Messenger v8.0 shared a folder with me and Messenger prompted me if I wanted to use a virus scanner. It uses the virus scanner reviewed a few weeks ago.

http://www.noelwatson.com/blog/PermaLink,guid,212b4ad3-ae6b-4d99-8618-b410bd41a60e.aspx

http://safety.live.com/site/en-US/default.htm

You can configure to use other virus scanners

I'm assuming that the virus scanner will be released at the same time (if not before) Messenger 8.0