As a follow-up to my recent post on CAPTCHA alternatives, below are some more resources and developments on the topic:
Coding Horror has a post on CAPTCHA effectiveness and how it’s a “necessary evil.” Be sure to read through the comments for some added discussion and insight.
A recent post on Modern Blue suggests a CAPTCHA alternative that uses CSS to stop spammers. The trick is to include an extra field in the form that is hidden from humans using CSS. Spam bots will still see the field and almost always try to enter something into it. Humans, on the other hand, will not see the form field in their browser and will therefore leave it blank. When processing forms, any submissions that have data in the special field can be tossed out as spam. The post’s comments indicate that this method works very well.
Finally, a story posted to Slashdot earlier this week asks the question “Have Spammers Overcome the CAPTCHA?” It seems that spammers are managing to generate tons of new Hotmail accounts. Since Hotmail uses CAPTCHA to block automated creation of accounts, it may be that someone has found a way around it.
