The Sober worm variant is expected to reappear on Thursday, January 5, 2006. This particular worm is political in nature coinciding with the 87th anniversary of the founding of the Nazi party. Always beware of what you open in email. Worms are particular pests because they are so easily spread through networks. They can sit silently on a computer and send out spam without the user's knowledge.
Make sure your antivirus software is always up to date.
You can read the story by Michael Kahn at Reuters at Yahoo News.