Abstract

From: http://gursevkalra.blogspot.com/2011/11/captcha-hax-with-tessercap.html

With the goal of creating a tool that can help security professionals and developers to test their CAPTCHA schemes, I conducted a research on over 200 high traffic websites and several CAPTCHA service providers listed on Quantcast’s Top 1 Million Ranking Websites .

During the same time frame, students at the Stanford University also conducted a similar research (PDF) . Both research works concluded the obvious:

An alarming number of CAPTCHAs schemes are vulnerable to automated attacks.