I used to use the Stop Spammers extension on WordPress to deal with spam. It was okay, but I realized it was buggy. (And no, I'm not reporting the bug. I'm too lazy for this shit, and it ain't my problem anymore.)
I switched to Antispam Bee and I find it much better than Stop Spammers ever was. I don't even see most of the spam it catches (unless I open up the Spam category on my instance) because the idiot spammers fill a hidden field that causes the extension to immediately decide that this is spam.