CAPTCHAShort for completely automated public turing test to tell computers and humans apart, a technique used by a computer to tell if it is interacting with a human or another computer. Because computing is becoming pervasive, and computerized tasks and services are commonplace, the need for increased levels of security has led to the development of this way for computers to ensure that they are dealing with humans in situations where human interaction is essential to security. Activities such as online commerce transactions, search engine submissions, Web polls, Web registrations, free e-mail service registration and other automated services are subject to software programs, or bots, that mimic the behavior of humans in order to skew the results of the automated task or perform malicious activities, such as gathering e-mail addresses for spamming or ordering hundreds of tickets to a concert.
In order to validate the digital transaction, using the CAPTCHA system the user is presented with a distorted word typically placed on top of a distorted background. The user must type the word into a field in order to complete the process. Computers have a difficult time decoding the distorted words while humans can easily decipher the text. Some CAPTCHAs now use pictures instead of words where the user is presented with a series of pictures and asked what is the common element among all of the pictures. By entering that common element, the user validates the transaction and the computer knows it is dealing with a human and not a bot.
The word public in the term refers to the fact that the algorithm used is made public instead of being held secret. The idea is that breaking the scurity of a CAPTCHA depends on artifical intelligence; discovering the algorithm itself does not defeat the security measures. The term was coined by Luis von Ahn, Manuel Blum and Nicholas J. Hopper of Carnegie Mellon University, and John Langford of IBM in 2000.
- Watch Datamation's editor James Maguire moderate roundtable discussions with tech experts from companies such as Accenture, Dell, Blue Jeans Network, Microsoft and more »
Learn about each of the five generations of computers and major technology developments that have led to the current devices that we use today. Read More »Small Business Marketing's Greatest Hits
The following compilation of small business marketing tips highlights some of the expert advice published over at Small Business Computing. Read More »13 Best Free Android Apps
From secure messaging to document editing, our top free must-have apps have been rated, reviewed and named the best free Android apps of 2015. Read More »
With cost and security in mind, we look at five cloud storage options that will suit the needs of most home and SMB owners. Read More »Windows 10 Tips for Desktop PC
Five basic tips to help you customize Windows 10 on your desktop PC. Read More »29 Free Android Apps for Cash-Strapped Students
From wacky alarm clocks to lecture hall tools and after class entertainment, these Android apps are a good fit for a student's life and budget. Read More »