With the popularity of the CAPTCHA images on comment forms and the like these days, it's always interesting to see what kind of other solutions that people are coming up with. One such solution is mentioned in this post on Lukas Smith's blog today.

The observant of you may have already noticed this. But I changed the CAPTCHA in my blog from the rather obnoxious and very hard to read image generated by the code I picked up from the PEAR::Text_CAPTCHA sample to a fairly simple math problem. It seems to hold off spam well for now. Expect the math problem to increase in difficulty once I get spam (or stupid comments) but for now all is well.

While it's not quite as secure, it could be made more so quite easily, plus it's not something that you'd need a special module for. It updates each time the page is reloaded to help deter would-be comment spammers...