Comment spam is a growing problem that is not expected to go away anytime soon. WordPress come packaged with some nice features to help prevent comment spam. By adding offenders to your blacklist you can affectively keep out known spammers. This plugin takes the prevention of comment spam a step further by requiring a second step in order for visitors to post a comment.
An e-mail will be sent to the visitors e-mail address requiring them to click a unique link to verify the comment is legitimate. This acts very much like a double opt-in mailing list.