Contributed by: Brian Clark
What are these random letters I have to type before I can submit a form on a web site?
Google, Yahoo! and others have been using this kind of barrier for a while now, and while, at times, it may be frustrating, there is a method to their madness. Its called CAPTCHA, or Completely Automated Public Turing test to tell Computers and Humans Apart. As the name implies, this tests to ensure a real person is filling a form, and not something automated.
Why go through all this trouble?
Other individual sites use CAPTCHAs to combat spam that is sent to the site owners through their own contact forms. Using this method, it ensures that their visitors’ emails are not lost in a flood of trash.
CAPTCHA techniques aren’t fail-proof, but they are evolving as fast as attackers find ways to have their automated programs, believe it or not, interpret CAPTCHA images without the aid of a human.