1. CAPTCHA Presentation by Annette Tsui, Section 2

2. What is CAPTCHA? zCAPTCHA: Completely Automated Public Turing test to tell Computers and Humans Apart  Introduced by Alan Turing in 1950 - “If a computer’s performance was indistinguishable from a human, it could be deemed intelligent.” zStill not able to do completely, but programs have been developed that are able to pass tests that humans can pass

3. Types of CAPTCHAs zVisual-based and Sound-based zVisual-based examples: yGimpy, EZ-Gimpy, Gimpy-r, Pessimal Print, Baffletext ySound based: Sounds CAPTCHA used in Hotmail®, Yahoo! ®, and Altavista® new login accounts

4. Visual-based CAPTCHAs Yahoo!® CAPTCHA (EZ-Gimpy) Gimpy CAPTCHA Source: http://www.captcha.net

5. Visual-based CAPTCHAs Pessimal Print CAPTCHA Baffletext CAPTCHA Source: http://www2.parc.com/istl/projects/captcha/captchas.htm

6. Further Information zThe CAPTCHA Project: http://www.captcha.net zPARC (Palo Alto Research Center) website about CAPTCHAs: http://www.parc.xerox.com/research/istl/project s/captcha/ zGreg Mori’s web page about his attack on Gimpy: http://www.cs.berkeley.edu/~mori/gimpy/gimpy.html