I currently have a website in which I allow people to leave comments. I have it set up to where I have to approve all comments before they show up on my site. However, so many are spam, and or people coming back to my site every couple of days posting virtually the same comments, just trying to build back links. I use Word Press for my site. Is there a plug in or something that I can use that will recognize the spam, so I don't have to spend so much time filtering it manually?