I found this suggestion on Novell's KB

5) http://*/*.mp3
This example demonstrates how to block access to a file type. This can
be
used to block downloading of, as in this example, MP3 files. Please
note
that in this example only http downloads are blocked. Another rule for
ftp
downloads would be needed.5) http://*/*.mp3
This example demonstrates how to block access to a file type. This can
be
used to block downloading of, as in this example, MP3 files. Please
note
that in this example only http downloads are blocked. Another rule for
ftp
downloads would be needed.

What is that ftp rule they are referring to? because I need it.