Spam hell

As if regular old spam trying to get me to enlarge body parts I don't have isn't bad enough... What it looks like is that someone else has been sending out spam using my email address, so that I get the bounced messages (and presumably the complaints although I haven't seen any of those yet). I've been getting over a hundred of these a day--and they all have an attachment! Grrrrrrrrr!

Seriously, is there anything I can do about this? I'm guessing not.

I suppose it might be a virus on someone else's computer? (I use a Mac for email so I don't think it's one on mine.) Should I tell my isp? I'm assuming they can't do anything about it either.