InfoQ: Spam Prevention without CAPTCHA Images

InfoQ: Spam Prevention without CAPTCHA Images:

The ASP.NET AJAX Control Toolkit (formally known as AJAX) offers a control that reduces spam on web logs and forums without requiring users to enter a CAPTCHA.

The NoBot control uses three techniques to detect bots.

* First, it offers a framework for a challenge/response in the form of a client-side JavaScript calculation. This will filter out bots that don’t support JavaScript.

* Second is a minimum delay. The idea behind this is if you know that users cannot possible fill out a form in less than 2 seconds, you can assume they are bots.

* Finally it can limit the number of submissions from a given IP address in a time period. For example, a human isn’t likely to make 5 posts in a single minute.

Interesting setup, but….

It works only because it encourages spammers to go to the less-protected sites. Of the three techniques, the 2nd and third are both trivial for a bot to circumvent — should the spammer care to. They’re little more than security by obscurity, and I don’t think worthy of even bothering with. Faking IP addresses and adding sleeps are trivial for a spammer to do.

As to the first — given spammer’s willingness to improve their technology as the anti-spammer technology does, it’s probably only a matter of time.

I was hopeful, but to me, this mostly seems capable of instilling a false sense of security, I don’t think it really can replace the CAPTCHA (and I hate them…. I’d love to find an alternative).

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