Resource links for Security Now! Episode #101:
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Are You Human?
- Wikipedia's excellent CAPTCHA coverage (and references)
If CAPTCHA interests you, be sure to read Wikipedia's excellent coverage of the topic. And don't miss their extensive references at the bottom of the page for additional material.
- The W3C's 'anti-CAPTCHA' page
The discussion on this page highlights a number of useful points about the problems and troubles with CAPTCHA systems — predominantly relating to their inherently accessibility-discriminating side effects. But it does so with such a slant that it seems 'anti-CAPTCHA'. It also offers little in the way of useful alternatives.
However, one useful observation it makes is that not all sites require an equal degree of CAPTCHA "protection", so that, perhaps, CAPTCHA should not be used indiscriminantly.
Visual CAPTCHA Cracking Sites:
- PWNtcha - captcha decoder
"PWNtcha" stands for: Pretend We're Not a Turing Computer but a Human Antagonist. This page was created by someone who has spent a great of time analyzing and cracking many of the most popular public site CAPTCHAs around. He writes decoding code to do this, shows his code's success rate for each of the different CAPTCHA styles, and critiques the strengths and weaknesses of each style.
- Breaking a Visual CAPTCHA
Here, some serious university computer vision guys tackle (successfully) the challenge of employing well-known computer vision techniques to the challenge of cracking CAPTCHAs. This page also has plenty of great examples. Also checkout this harder version of Gimpy
- Using AI to beat CAPTCHA and post comment spam
Unfortunately, this hacker has badly upset people by using his technology to actively post comment spam. But his page is useful and interesting since he goes into some level of detail explaining the approaches he has taken and showing the various steps of image processing his system uses.
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