Are you Human? (Sorry, I had to ask) Ecaterina Valică http://students.info.uaic.ro/~evalica/

Example: Filling out a form Google uses CAPTCHA for Gmail accounts:

Inventor Luis von Ahn ( 1978 - ) Photograph by Mike McGregor

Other : Mathematical CAPTCHA

Other : Mathematical CAPTCHA

Other: Jumble Game

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Guidelines: Accesibility Hard to read CAPTCHAs:

Guidelines: Accesibility Worst CAPTCHAs:

Attacks – SimpleOCR Engine 2002

Porn Companies (October 2007)

reCAPTCHA

The ESP Game Player 1 Guessing: CAR Guessing : HAT Guessing: KID Success! You agree on CAR Player 2 Guessing : BOY Guessing : CAR Success! You agree on CAR

http://gwap.com/gwap/

http://gwap.com/gwap/ ESP Tag a Tune Matchin

http://gwap.com/gwap/ Squigl Verbosity