CAPTCHA: Telling Humans and Computers Apart Automatically A CAPTCHA is a program that protects websites and other online service against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text, but current computer programs can't. The term CAPTCHA (for Completely Automated Public Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel
