CAPTCHA evokes sympathetic (aka correct) response
Tuesday, October 9, 2012 - 05:30
in Mathematics & Economics
(Phys.org)—CAPTCHAs by definition (stands for Completely Automated Public Turing Test to tell Computers and Humans Apart) are gotcha tools that are used to spot automated-attack attempts posing as people. CAPTCHA programs are designed to plant character strings as entry codes, asking Internet sign-up users to repeat the string of letters to confirm the users are humans. The CAPTCHA in a broader sense protects websites against bots by generating and grading tests with distorted characters, tests designed for humans to pass and for machines to fail. A CAPTCHA image shows a random string. Then the user types it back to enter a site or to submit a form.