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 (kăp′chə) Computers
A security feature, as on a webpage, that attempts to distinguish between legitimate human users and bots by requiring users to perform a mildly challenging task such as deciphering distorted text.

[Acronym of c(ompletely) a(utomated) p(ublic) T(uring test to tell) c(omputers and) h(umans) a(part), coined in 2000 by the researchers who developed the security feature and intended to suggest a colloquial pronunciation of capture.]


(Communications & Information) a test in which the user of a website is asked to decipher a distorted image, used to protect the website against automated attacks
[C21: acronym for C(ompletely) A(utomated) P(ublic Turing Test to) T(ell) C(omputers and) H(umans) A(part)]
References in periodicals archive ?
CAPTCHA is informed by a basic cryptographic principle: it proves you are who you are by making a challenge that forces you to manifesta response that only you can have.
94 CAPTCHA logic-puzzle filters are only the most recent development, a temporary hindrance that advocacy group service vendors will soon bypass.
Some districts require that the CAPTCHA logic puzzle be solved, but others still redirect you to the representative's Web site.
For other tests and applications, go to the CAPTCHA Project site at www.
Separately, the"I am Robot" researchat last year's BlackHat revealed how researchers broke the latest semantic image CAPTCHA and compared various machine learning algorithms.
Less time spent figuring out confusing CAPTCHA, or proving you're not a robot, would certainly equate to more time consuming content in the internet.
The background noise is added to CAPTCHA image not related to context but making context of CAPTCHA harder to read.
Shirali-Shahreza, "An Anti-SMS-Spam using CAPTCHA," Proceedings of International Colloquium on Computing, Communication, pp.
New DNSSEC Security Measure, Along with Existing CAPTCHA, Help Defend Computers from Web Hacking, Phishing and Other Growing Security ThreatsD-Link Middle East & Africa, the end-to-end networking solutions provider for consumers, businesses, and service providers, today announced it is the first in the industry to enhance its router security to a higher level of protection by incorporating both CAPTCHA and DNSSEC to guard against hacking, worms, viruses and other malicious Web attacks.