This article shows how you can effectively protect your website against spam-submissions in comments.

In order to improve the interaction with the visitors of this website, I allowed anonymous users to post comments to all published stories. Since feedback is quite low, I enforced administrator approval of all comments to stay in full control.

However, shortly after enabling comments for anonymous users, I received more and more emails telling me that new comments were posted which needed my approval.

CAPTCHA to the rescue!