Captcha

[David]

Sadly, image verification is now a fact of life on the web. Whether you're adding a comment to a Blogger blog or registering for membership with a vBulletin forum, you'll be prompted to read an image with some jumbled letters and type those same letters out into an edit box. This proves that you're human.

I can personally testify to the effectiveness of the approach. Prior to my moving the CADTutor forum over to vBulletin (from phpBB ), I was spending half-an-hour each day deleting spam members and spam posts, adding mail services to a banned list and banning IP addresses. vBulleting uses the latest CAPTCHA system and since moving, spam has dropped off to nil. Not one. That's pretty impressive.

I'm still worried though. Image verification is fine for most of us but what about the partially sighted? The image verification system may be secure but it's not accessible - until now.

Those clever people at CAPTCHA now have an audio version of the system for the visually impaired. I haven't actually seen this implemented anywhere yet but it is possible.

More information: http://www.captcha.net/
Wikipedia: http://en.wikipedia.org/wiki/Captcha

[francis]

I've seen it implemented, but I can't remember where. It might be on Blogger blogs that use captcha to screen user comments. From memory, there's the text followed by a little wheelchair icon. Might need to try and tempt my brother into upgrading the forum on his site.

[francis]

Yeah, here you go, Blogger have it on their site (http://www.blogger.com/comment.g?blogID=24151979&postID=115341295050659974). Click the wheelchair to hear the code.

[David]

:"> Gosh, you know, I'd seen that and not really noticed it or realised what it was for. OK, so now we can start aking it to be implemented on other applications. I'm just off to vBulletin.com ;)