Over the last couple of weeks I have started having some problems with spam showing up on various pages where I allow the a visitor to post comments. The message is always the same across all the pages. To help prevent this type of spam the visitor must register with the site and have their email address validated by clicking an activate link in an email sent to them. In the registration form there is also a Captcha. Not sure why they are choosing to spam this site as I remove any html from the comments. The IP the requests originate from were are all in Africa. My quick solution is that I am blocking traffic from in the offending IP ranges. This is only a temporary solution as eventually I figure I will start having problems with IPs originating in the US.
The other day I started searching Google for possible solutions. One option was to find a Captcha library that was more difficult to crack than the one I am currently using. In the search I came across a list of the Top 10 Worst Captchas. These are were all a little extreme, but would definitely do the job. I doubt I would get any comments with some of these.
After searching for a while I settled on reCaptcha which is a project at Carnegie Mellon University. They have libraries for the popular web languages and some plugins for applications. One of them is for WordPress which I installed earlier today. A quick blurb about reCaptcha project:
Over 60 million CAPTCHAs are solved every day by people around the world. reCAPTCHA channels this human effort into helping to digitize books from the Internet Archive. When you solve a reCAPTCHA, you help preserve literature by deciphering a word that was not readable by computers.
I’ll let you know if I have any issues with the PHP version. From the documentation it is pretty straight forward and I don’t have to deal with the image libraries anymore like I had to with my previous Captcha library.