Filed in archive Information About on July 25, 2010

CAPTCHA-Telling Humans and Computers Apart

© andrewsteinborn

The foundation of CAPTCHA technology lies in the Turing Test which was proposed by Alan Mathison Turing, to test whether a computer is capable of human like thought. CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart and is a type of automated Turing Test. It is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. The term was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University.
CAPTCHAs have several applications in practical security including:
• Preventing comment spam in blogs
• Preventing website registration
• Protecting email addresses from scrapers
• Preventing dictionary attacks
• Search engine bots
• Worms and spam
The spammers or hackers have dedicated time and energy to break the CAPTCHAs as they are a barrier between their goals. Eventually, computers and humans may start to perceive puzzles the same way, making tests like CAPTCHA useless.