[Exim] global killfile

Hello,

I searched the archives and didn't come up with anything obvious so I
thought I'd ask the wise people on this list how to do this seemingly
trivial operation..

The volume of spam seems to be going up every week and I'd like to
implement a global killfile for incoming mail that is processed before
it is delivered to the mail list manager, local users, aliases;
before anything.

Right now I have a procmail filter set up on my personal mail that does
a simple grep (no regex) on the header of the email and sees if there
are any case-insensitive matches in my killfile (which contains snippets
of headers, email addresses, etc one per line)

I'd like to set something similar up in exim and have those messages
nuked & logged, or dumped into a file... I don't plan on going through
the matched messages, don't have time for that, but if there is a way to
easily freeze such messages and then kill them all in one fell swoop
that would be OK. Having it logged somewhere would be nice to debug if
legit messages are getting dropped.

I'm using exim 3.13 (I know I know...)

I've looked at SpamAssassin, I might install that later but I just want
something very simple for now.

Thanks!
Skye