CAPTCHA

CAPTCHA, which stands for "Completely Automated Public Turing test to tell Computers and Humans Apart," is a type of challenge-response test used in computing to determine whether the user is human or not. This tool is commonly used on websites to prevent automated software (like bots) from performing actions that could potentially be abusive or harmful, such as creating accounts, posting spam, or conducting Brute Force Attack|brute-force attacks.

CAPTCHA presents a challenge that is usually easy for humans to solve but difficult for automated systems.

Types of CAPTCHA:

• Text-based CAPTCHA: Displays distorted text that a user must correctly enter. The distortion is designed to confuse automated text recognition software.
• Image-based CAPTCHA: Requires users to identify and click on specific items in an image (like all pictures with traffic lights).
• Audio CAPTCHA: Plays a series of letters or numbers as audio for the user to enter. This type is often used as an alternative for visually impaired users.
• Mathematical or Logical CAPTCHA: Asks the user to solve a simple math problem or answer a logic question.
• reCAPTCHA: A popular service by Google, it includes the "I'm not a robot" checkbox and sometimes requires image identification. Advanced versions work in the background, analyzing browsing behavior to detect bots.

CAPTCHA is effective at reducing spam, automated form submissions, and brute-force attacks by making it difficult for bots to complete the required tasks. CAPTCHA can sometimes be frustrating for users, especially if the challenges are too difficult or inaccessible.

Traditional CAPTCHAs (like distorted text) can be challenging for users with visual impairments, leading to the development of more accessible alternatives. Improvements in AI and machine learning have led to automated systems being able to solve certain types of CAPTCHAs, which necessitates continuous evolution of CAPTCHA methods.