How to reject all mails with docs attached?

[Thomas Barth]

Hi,
for a week or so I get a lot of mails with bills as doc-documents and 
Spamassassin is actually not able to mark it as spam. The documents 
contain a macro. AMaVis is configured to reject all spam-mails directly 
(no store&forward). How can I configure Spamassassin to mark all mails 
with doc-documents attached as spam? I need some time for preparing an 
complete update of my first mailserver (Debian / Postfix / courier / 
AMaVis / Spamassassin / ClamAV).

Thomas B