more direct solution might be...

I tell my friends that e-mail me to include a catch phrase, nickname, etc, that they must type into the body of a mail themselves when they include an attachment. If I don't see that specific thing, i never open the attachment... It may seem 'assholish' to ask for such a thing, but upon explaining why, they always understand (and usually ask for the same in return). Trust me...you won't be fooled by "pics from my party" or "hey check this out" crap ever again...

Ouroboros

edit: here is some info about it... http://antivirus.about.com/library/weekly/aa111201a.htm

O