[Mailman-Users] Quick and dirty anti-Klez procmail?

[LuKreme]

I don't want to restrict all attahments on one of my lists, but I do 
want to stript those x-midi or x-wave klez viruses.

Does anyone have a quick and dirty procmail recipe to do that?  I tried:

:0BH
* Content-Type: audio/x-midi
/dev/null

:0BH
* Content-Type: audio/x-wav
/dev/null

in /etc/procmailrc but the messages where still delivered.