Centralized Email Virus Filters?

Matt Hamilton asks: "With yet another email trojan/virus going around (Naked Wife) I am looking for some way to simplify filtering of these messages. I currently run Exim on our companies servers and have a filter that filters about 20 virii based upon subject lines and strings contained in the body. Very simple, but works against alot of mass-email virii. I was wondering, is there a centralised database of current email virii/trojans and their subject/body signatures that can be exported to various MTA filtering mechanisms (sendmail, exim, procmail, etc.). Or perhaps a step further, some sort of central DB that can be accessed directly realtime by the MTA (similar to RBL, ORBS, etc.) so that updates are automatic."