When registering on the computer more than often one has to copy some letters that have been obscured. Why is this done?

McGruff

It is to prevent a machine from reading the letters, so some automated program can't register accounts. A human has to be at the keyboard to decipher the code. The word puzzles are known as CAPTCHAs, short for "completely automated public Turing tests to tell computers and humans apart." Computers can't decipher the twisted letters and numbers, ensuring that real people and not automated programs are using the Web sites. http://www.ibtimes.com/articles/20070524/blather-to-books.htm A CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. The term CAPTCHA (for Completely Automated Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo. http://www.captcha.net/ Sep 14 07, 11:51 PM