WordPress Plugin: Spam Karma
The ultimate comment spam killer and filter. Spam Karma works by running every new comment through a battery of filters and checks. Each of which increase or decrease the commentâ€™s â€˜Karmaâ€™ value. Depending on the final score, the comment is either: Approved, Discarded silently as spam (no email is sent to you, unless you specifically require it, but a digest is sent to you every X spams deleted), or placed in Moderation mode.