[Exim] filter help

I'm running exim 3.14
I have a small problem,

background:
A nasty person is sending huge ammounts of UBE to <random>@domains
they have set the message subject to be random, and the from
address is <random>@mydomain

The main problem is that I'm now getting thousands
of bounces.
My initial thought was to discard these messages
based on the subject by testing for Undeliverable/failure etc..
Are any special headers added to a bounced message ?
if so what are they ?

If anyone has any thoughts on this I'd would love to hear them
possible solutions especially :)


Tristan