Everything in this world has a name. We’ve always found it fun to learn the names of obscure processes and things that creep into existence while we are busy doing other things.
Have you signed up for anything on the Internet recently and been asked to identify a series of strange alpha-numeric characters? If so, you’ve been identified as a human being instead of a computer, thanks to a technology called “captcha.” Captcha? (a trademark of Carnegie Mellon University) is a sequence of distorted letters and numbers that can be recognized by humans, but not computers. Sometimes the backgrounds behind the letters are visually disturbed with colors and patterns, and sometimes the letters are distorted or connected in very strange ways. Here are some examples:
Whether you are applying for a Yahoo or MSN Hotmail account, a new domain name or an on-line registration for a rebate or a financial service, you will find examples of captcha guarding the door. Captcha is often the first step in authenticating you before you can become a member of a particular group or club.
Why is this important? If you have ever received SPAM, you are probably the victim of a rogue computer (and a rogue human) who has harvested your e-mail address to include you among its millions of members. Where it is instituted, captcha can stop “address harvesting” by its challenge/response test. It blocks a machine from signing up for accounts and then exploiting that service for a variety of attacks, from world-wide spamming to performing denial-of-service attacks, to distributing spyware and viruses.
Captcha prevents a computer from causing bogus traffic or harassing Google, Yahoo or MSN into placing a URL at the top of their search hierarchies.
The word “captcha” is an acronym for “completely automated public Turing test to tell computers and humans apart.” According to the Wikipedia,
“The term was coined in 2000 by Luis von Ahn, Manuel Blum, and Nicholas J. Hopper of Carnegie Mellon University, and John Langford of IBM. A common type of captcha requires that the user type the letters of a distorted and/or obscured sequence of letters or digits that appears on the screen. The test is administered by a computer, in contrast to the standard Turing test that is administered by a human . . .”
According to the authors of captcha, “it is an automated test that humans can pass but current computer programs can’t pass.” The Captcha Project? for telling humans and computers apart comes from Carnegie Mellon University School of Computer Science. The bad news is that bots are always improving so the tests continue to become more challenging for test designers. The good news is that every time a bot overcomes a captcha hurdle, text recognition software improves. This war between bots and legitimate information systems might be a win-win situation.
Even if an intruding bot (rogue computer) discovers the underlying computer code controlling the captcha program on the server, it cannot view the random letters and numbers the server generates in order to distinguish them. However, a human can, and inputting the correct digits will validate you. To state this again, only you and the server computer know the correct letters. An outside computer cannot distinguish them.
Therefore, if you try to use an automated computer to reserve 300 tickets for the next Stones or Mariah Carey concert or the next Atlanta Braves game, you probably won’t succeed. It occurs to me that captcha might even help prevent cascading Stock Market crashes by refusing automated sales once they reach a certain frequency.
Here’s one last example– no, don’t type anything, just look at it and remember the name of the process and the people who invented it so you can impress your human friends:
