1. 1. Alsaleh.M, Mannan.M, and van Oorschot P.C(Jan./Feb. 2012), “Revisiting defenses against large-scale online password guessing attacks,” IEEE Trans. Dependable Secure Comput., vol. 9, no. 1, pp.128–141.
   2. Biddle.R, Chiasson.S, and van Oorschot.P.C(2012), “Graphical passwords: Learning from the first twelve years,” ACM Comput. Surveys, vol. 44, no. 4.
   3. Bonneau.J(Jun. 2012), “The science of guessing: Analyzing an anonymized corpus of 70 million passwords,” in Proc. IEEE Symp. Security Privacy, , pp. 20–25.
   4. Chellapilla.K, Larson.K, Simard.L, and Czerwinski.M(2005), “Computers beat humans at single character recognition in reading-based human interaction proofs,” in Proc. 2nd Conf. Email Anti- Spam, pp. 1–3
   5. Chiasson.S, van Oorschot.P.C, and Biddle.R(2007), “Graphical password authentication using cued click points,” in Proc. ESORICS,pp. 359–374.
   6. .Chiasson.S, Forget.A, Biddle.R(2008), and van Oorschot.P.C, “Influencing users towards better passwords: Persuasive cued click-points,” in Proc. Brit. HCI Group Annu. Conf. People Comput., Culture, Creativity, Interaction, vol. 1, pp. 121–130.
   7. Dirik.E, Memon.N, and Birget(2007), “Modeling user choice in the passpoints graphical password scheme,” in Proc. Symp. Usable Privacy Security, pp. 20–28.
   8. Davis.D, Monrose.F, and Reiter.M(2004), “On user choice in graphical password schemes,” in Proc. USENIX Security, pp. 1–11.
   9. Dunphy.P and Yan.J(2007), “Do background images improve ‘Draw a Secret’ graphical passwords,” in Proc. ACM CCS, pp. 1–12.
   10. Elson.J, Douceur.J.R, Howell.J, and Saul.J(2007), “Asirra: A CAPTCHA that exploits interest-aligned manual image categorization,” in Proc. ACM CCS, pp. 366–374.
   11. Gao.H, Liu.X, Wang.S, and Dai.R(2009), “A new graphical password scheme against spyware by using CAPTCHA,” in Proc. Symp. Usable Privacy Security, pp. 760–767.
   12. Golle.P(2008), “Machine learning attacks against the Asirra CAPTCHA,” in Proc. ACM CCS, pp. 535–542.
   13. Golofit.K(2007), “Click passwords under investigation,” in Proc. ESORICS, pp. 343–358
   14. .Joshi.N (2009, Nov. 29). Koobface Worm Asks for CAPTCHA [Online]. Available: http://blogs.mcafee.com/mcafee-labs/koobface