Simple system-wide keyword email filter?

Is there any aspect of the cPanel system that can be used as a system-wide, keyword based anti-spam filter?

Let's say that I wanted to send to /dev/null all incoming email with the word "viagra" in the subject line, and do this for every single email address hosted at the server. How would I do this?

Thanks much.


By the way, I had been using /etc/antivirus.exim for this, but the rules I enter in this file no longer have any effect, even though the following IS in the /etc/exim.conf file:

system_filter=/etc/antivirus.exim

Here is a sample of my rules in the above file, but again, none of this has any effect (and yes, this used to work fine):

# Exim filter
if error_message then finish endif
if
$message_headers contains "viagra"
or $header_reply-to contains "internetseer"
or $header_Subject contains "Buy and save"
or $message_headers contains "Buy and save"
or $message_headers contains "tpnet.pl"
or $message_body contains "Facebook_details"
or $message_body contains "mailbox utility"
or $message_body contains "module.zip"
or $message_body contains "balancechecker.zip"
or $message_body contains "remote-admin.net"
or $message_body contains "microsoftofficeupdate"
or $message_body contains "viagra"
or $message_body contains "phentermine"
then
save "/dev/null" 660
endif