Ok, I'll post something that's less likely to be taken as critical and more likely to be seen as helpful, which is more my intention.
Another forum I help moderate uses the services of this group to help stop spammers: Stop Forum Spam
They provide automated checking as well as the ability to add spammers by username, email address and IP address to a database.
I mention this as I have seen (and banned from my other forum) many a spammer that used sig lines to include their spam links.