Comment spam has been driving me nuts. I implemented a blacklist based fliter a while back which stopped a bunch of it, but ever week 100’s of bogus comments got through because the blacklist was not updated fast enough.
So as of last night I have implmented a CATCHPA solution on the comment posting form. CATCHPA stands for “completely automated public Turing test to tell computers and humans apart”. The term “Hip” is also used “Human Interaction Proof”.