In Ripsnort's defence, I would like to point out that this particular virus does not come from the person it appears to! It chooses the Sender's name at random from the address book, and sends to others in the same address book.... so, although it is somebody you know who is supposed to have sent the email, it will in fact be someone else who has you both in their address book.
I have had several incidences of this worm - all caught on the way in by Norton Anit-virus - and most coming from people I know; however, I have not laid into these people, as I know it hasn't actually come from them and they are as innocent victims as we are in receiving it.
Like Sveno, I also use TheBat and, in conjunction with Norton Anti-Virus, have a very safe system.