CAPTCHA: The CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) has evolved from simple text-based puzzles to advanced reCAPTCHA systems, significantly enhancing online security by verifying user identity and blocking automated bots.

• About CAPTCHA: It helps keep websites safe from automated attacks and ensures that online services remain user-friendly by distinguishing humans from bots.
• Origin: Introduced in 2000s to combat fake accounts, spam, and data theft caused by bots.
• Working Principle: CAPTCHA is based on the Turing Test, proposed by Alan Turing in the 1950s.

o It presents puzzles that are easy for humans but hard for computers, such as recognising distorted letters or selecting images with specific objects.

• Security Applications: Used on business, e-commerce, and financial websites to stop spamming, fake account creation, and credit card theft.

o Plays a role in account recovery, online surveys, and polls to ensure only real users participate.