CAPTCHAs--the squiggly-word or noisy-audio puzzles that everyone encounters on the Web-- are used to thwart automated attacks because they are supposed to be much easier for people to solve than computers. But are they, really? Come to this talk to hear how our techniques broke real world CAPTCHAs from Microsoft, Yahoo, Slashdot, Recaptcha and Ebay, and learn how to design secure CAPTCHAs.