Dissuading Spammers

Hello,

I have the plugins “Trackback Validator” and “Comment Authorization” to prevent spamming of trackbacks and comments, respectively. Both do their jobs very well.

Nevertheless, each morning I find 30-40 comments awaiting authorization (since they are authorization-by-email, the auth requests end up in my gmail spam folder.) It takes me literally 10 seconds to delete them all, but I am getting tired of giving bandwidth to these jackasses.

Are there blacklists which work well? Perhaps a blacklist/authorization (“You are viewing this site from an IP address which has been used to send spam; please type the letters you see above in order to proceed”) would work. Or is there some other way of dissuading spammers from even making the attempt?

Thanks
Reuben