Finally, I have upgraded my BlogEngine site from 1.4.5 to 1.5.0.7 and have added hidden spam extension to my blog.

I was spending around 10 minutes every day to remove spam comments, although they flatter me and my blog which I like ;).

I would like to share with you my search results about the spam filter:

1.Blacklist Extension: which simply depends on the author name and blocks it.
2.Commentor: which uses service to determine if the comment came from spammer or not and also provide you with the ability to approve and disapprove group comments.

I do recommend Commentor although it is more sophisticated than the former one but still easy to use and provides better service.

Blacklist Extension and Commentor are the links for the two extensions to download and see how to use them.

Have fun.