To solve Yahoo’s problem, von Ahn and Blum created a computer program that 1) generated a random string of text, 2) generated a distorted image of that text (called a ‘CAPTCHA code’), 3) presented the image to the user, and 4) asked the user to enter the text into a form field, and then submit entry by clicking a check box next to the phrase ‘I am not a robot.’ Because optical character recognition (OCR) technology of the time struggled to decipher such distorted text, bots could not pass the CAPTCHA challenge. This team was inspired to work on the technology by a Yahoo executive who delivered a talk about the company's issues with spambots signing up for millions of fake email accounts. But the term CAPTCHA was coined in 2003 by a group of computer science researchers at Carnegie Mellon University led by Luis von Ahn and Manuel Blum. Researchers at the IT company Sanctum filed the first CAPTCHA-style system in 1997. For example, computer scientists working for the search engine AltaVista wanted to stop bots from adding malicious web addresses to the company's link database. Each group was working to combat the widespread problem of hackers using bots to carry out nefarious activities on the internet. The earliest forms of CAPTCHA technology were developed by several different groups in parallel during the late 1990s and early 2000s. By meeting the challenge, users they are human and are allowed to continue their activity on the website.
Many web sites require users to complete a CAPTCHA challenge before logging into an account profile, submitting a registration form, posting a comment, or performing some other action that hackers might use a bot to perform. Newer iterations of CAPTCHA technology use AI-driven behavioral and risk analyses to authenticate human users based on activity patterns rather than a single discrete task. Traditional CAPTCHAs asked users to read and correctly retype distorted text that could not be interpreted by optical character recognition (OCR) technology. CAPTCHAs prevent scammers and spammers from using bots to fill out web forms for malicious purposes.
CAPTCHA, an acronym for "Completely Automated Public Turing Test* to Tell Humans Apart," refers to various authentication methods that validate users as humans, and not bots, by testing users with a challenge that is simple for humans but difficult for machines.
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