Jeremy Elson, John R. Douceur, Jon Howell, Jared Saul. Asirra: a CAPTCHA that exploits interest-aligned manual image categorization. In Peng Ning, Sabrina De Capitani di Vimercati, Paul F. Syverson, editors, Proceedings of the 2007 ACM Conference on Computer and Communications Security, CCS 2007, Alexandria, Virginia, USA, October 28-31, 2007. pages 366-374, ACM, 2007. [doi]
Abstract is missing.