Stuart Sequeira

Block comment spam (up to 98% of it !) by inserting a question and answer field on your comment forms. No more wasting your time emptying out pages of spam messages just to get to the real comments from real visitors!
You can create your own simple question, like “What is 1 plus 1?” and the commenter must supply an answer on the comment form. If the commenter can’t answer the question correctly, this great little plugin blocks the comment from getting into your website.
Thanks to Andrew Kurtis and his team at Web Hosting Hub for translating this plugin into Spanish!
With the recently added blocked-spam counter, we collected data on our test site that blocked 798 spam comments and allowed only 14 through – a 98% success rate!

Comment Gatekeeper

Block spam comments by adding a simple question and answer field to your comment forms.

Pippin Williamson

Modifies the Empty Spam action in WordPress to process the spam deletion in batches, allowing you to delete thousands or even hundreds of thousands of spam comments at once without killing your server.
Have you found a bug or have a suggestion or improvement you’d like to submit? This plugin is available on <a href="https://github.com/pippinsplugins/batch-comment-spam-deletion" rel="nofollow ugc">Github</a> and pull requests are welcome!

Batch Comment Spam Deletion

Modifies the Empty Spam action in WordPress to process the spam deletion in batches instead of all at once.

Comment Gatekeeper vs Batch Comment Spam Deletion