Recommend Anti-Spam Plugins?

Hi;

I have Spam Karma 2.

Getting tired of those reports with requests to confirm spam I thought I would install a plugin that would make my comment authors answer an arithmetic question before posting.

I’m still getting spam and spam that is making through spam karma2.

I doubt that people are spamming by hand ( it was on OLD posts ) so I guess spambots can now add.

Can anyone suggest other plugins that would slow spam bots down?

Thanks