We recently got hit by the Bugbear virus. As a result I installed [MailScanner](http://www.sng.ecs.soton.ac.uk/mailscanner/), [SpamAssassin](http://www.spamassassin.org/) and [Razor](http://razor.sourceforge.net/) on our work mail server and they now scan and process all incoming and outgoing mail. I can't recommend this trio of tools highly enough. Not only did they catch further BugBear hits, they also tag over 90% of the spam I receive so I can filter to trash. Go get em!