How the virus does it I don't know but it manages to post messages to Usenet. The messages I have seen are HTML pages that appear to come from Microsoft. They have an attachment. Do not open that attachment! If possible do not open that mail.
If you are using MSOutlook Express be sure you have set you security settings right. Be sure you have the latest updates on your machine and use a virusscanner.
Microsoft never sends patches or updates by e-mail and Usenet!
Now I need an excuse to make this on-topic again. What about the C6?