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CAPTCHA is the abbreviation of "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a method to distinguish whether a user is a computer or a human. The company's fully automatic program. It can prevent: malicious cracking of passwords, ticket fraud, forum flooding, and effectively prevents a hacker from using a specific program to violently crack a specific registered user from making continuous login attempts. In fact, using verification codes is a common method for many websites now. We use This function is implemented in a relatively simple way.

This question can be generated and judged by a computer, but only a human can answer it. Since computers cannot answer CAPTCHA questions, the user who answers the questions can be considered a human.

The term CAPTCHA was first proposed in 2002 by Louis von Ahn, Manuel Blum, Nicholas J. Hopper of Carnegie Mellon University and John Langford of IBM. Carnegie Mellon University attempted to apply for this term to be a registered trademark, but the application was rejected on April 21, 2008. A commonly used CAPTCHA test is to ask the user to input text or numbers displayed on a distorted picture. The distortion is to avoid being automatically recognized by computer programs such as optical character recognition (OCR, Optical Character Recognition). alphanumeric and loses its effect.

Because this test involves computers testing humans, rather than humans testing computers as in the standard Turing test, people sometimes call CAPTCHA a reverse Turing test. For people with disabilities who cannot see images, an alternative method is to use voice to read the alphanumeric numbers. In order to prevent voice recognition from analyzing the sound, the content of the sound will be noisy.