Elie Bursztein, Matthieu Martin, John C. Mitchell. Text-based CAPTCHA strengths and weaknesses. In Yan Chen, George Danezis, Vitaly Shmatikov, editors, Proceedings of the 18th ACM Conference on Computer and Communications Security, CCS 2011, Chicago, Illinois, USA, October 17-21, 2011. pages 125-138, ACM, 2011. [doi]
Abstract is missing.