"Klez" Worm Running Rampant
Set to wreak havoc March 6th, 2002, the Klez worm has been upgraded to a level 3 threat by Symantec's security response team.
This worm exploits a known security hole in Outlook Express, specifically the versions bundled with Internet Explorer 5.01 and 5.5. There is a patch available to fix the directly affected versions, or you may install the latest cumulative patch which patches all known security vulnerabilities affecting Internet Explorer.
In the meantime - update those anti-virus definitions!