CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) works by presenting challenges that are easy for humans to solve but difficult for automated bots. Here are the common types of CAPTCHA and how they function:
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Text-based CAPTCHA: Users are shown distorted text or numbers that they must type into a field. The distortion makes it hard for bots to recognize the characters.
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Image-based CAPTCHA: Users are asked to select specific images from a grid (e.g., "Select all images with traffic lights"). This requires visual recognition that is challenging for bots.
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Audio CAPTCHA: Users listen to a series of spoken letters or numbers and must enter them correctly. This is useful for visually impaired users.
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reCAPTCHA: A more advanced version developed by Google, which often requires users to check a box ("I am not a robot"). It analyzes user behavior (like mouse movements) to determine if the user is human. If uncertain, it may present additional challenges.
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Honeypot CAPTCHA: This method involves adding a hidden field to a form that should remain empty. Bots typically fill out all fields, while human users will leave it blank, allowing the system to identify and block bots.
By using these methods, CAPTCHA helps protect websites from automated abuse, such as spam submissions and brute-force attacks.
