Dunno if it is possible on CDZ, but would it help/be possible to ban certain IP addresses from registering on the forum?
A list of common spambot IPs is located at
http://www.gearhack.com/Articles/FightSpam/ and it is claimed there (as well as on wikipedia) that it can have some good result in fighting common spambots...
At the moment, spambots are really spiralling out of control on CDZ, it seems almost 50% of the spam produced on CDZ is now caused by bots, and we get several new "members" a day that need to be banned by the mods/admins on the same day they register.
