CAPTCHA has become a standard device to trap and block spam on sites like this one.
The idea is that if someone writes a computer program to drop spam comments on this blog, the computer program will be asked to solve a problem first. That problem (like “what letters are below in this squiggly image?” or “what’s 4+12?”) is not Turing-computible. So only a human being will solve it.
In the past 48 hours, I’ve had to remove two spam comments left by a human being. I can tell it was a human being because my site analysis showed a computer running Microsoft Internet Explorer 7, Windows XP, monitor resolution 1280-1024, located in China as the culprit. They solved the CAPTCHA first time. It must be a human. I’ve watched robots try and fail to solve my CAPTCHAs: They try 20 times in a row and then give up, and it never appears in my site analysis stats because no normal web browser ever loaded the page.
Time to try a new service. CAPTCHA is gone. In comes a new service called Mollom. Forget Tolkein. What this does is as follows: Someone leaves a comment. The contents of that comment are passed, encrypted, to Mollom’s servers. They check whether it’s “spam” or (wait for it): “ham”, and tell my website. I then block Spam, but let through all the Ham. Occasionally, Mollom returns “Not Sure” to my site, and then (and only then) you get a CAPTCHA to solve. See their how it works page for more information.
The upside: You can leave comments here without having to type in CAPTCHAs. Hurray. Especially as I know sometimes you patient visitors have to try a few times before answering the challenge successfully.
The upside: SPAM should be blocked automatically. If the SPAM-masters pay a human being to type it in, it will still be blocked.
Now all I need is lots of Ham please to test the thing. If you have problems, let me know.