I am testing a simplified plugin to validate spammers against the Stop Forum Spam database. It uses a different technique then the Stop Spammer Registrations plugin.
It checks against the spam db every time someone tries to login, register, comment, or ping. Rather than just refusing to leave the comment or register it crashes WordPress with a DIE command. This is a little more dramatic.
You can download the zip of the testing plugin at:
https://www.blogseye.com/stop-spammer-login.zip
I am still cleaning up some typos and adding a few features, but this is stable and I am using it here and at a few other of my sites.