dealing with bogon spam ?

[leslie at craigslist.org (Leslie)]

First off, I'm not certain if unallocated space in blocks less than a /8 
is properly called bogon, so pardon my terminology if I'm incorrect.

We're seeing a decent chunk of spam coming from an unallocated block of 
address space.  We use CYMRU's great list of /8 bogon space to prevent 
completely off the wall abuse, but the granularity stops at /8's. 
Obviously, I've written the originating AS and its single upstream 
provider (sadly without any response).  I'm not looking for a one time 
solution for this issue however -- I'd like to permanently block (and 
kick) anyone who's using unallocated space illegitimately.

How have you dealt with this issue? Does anyone publish a more granular 
listing of unallocated space? Does arin have this information somewhere 
other than just probing any given ip via whois?

Thanks!
Leslie
Craigslist Spam Hater