Rare
CAPTCHA
Test to determine whether a user is human
CAPTCHA
A CAPTCHA ( KAP-chə), a type of challenge-response Turing test, aims to protect computing user-interfaces. It attempts to deter bot attacks and spam by determining whether a user is a human. The term "CAPTCHA" was coined in 2003 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford. It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart". A historically common type of CAPTCHA (displayed as reCAPTCHA v1) was first invented in 1997 by two groups working in parallel. This form of CAPTCHA requires interpreting a sequence of letters or numbers from a distorted image. Because the test is administered by a computer, in contrast to the standard Turing test that is administered by a human, CAPTCHAs are sometimes described as reverse Turing tests. Two widely-used CAPTCHA services are Google's reCAPTCHA and Intuition Machines' hCaptcha. Cloudflare, a major website-security service provider, reported in 2021 that it takes the average...
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