Captcha

If you’re trying to get into a blog site or a Web site, you may have to prove you’re a human being.

If you’ve tried to sign up for a new e-mail account, post a comment on a blog, or participate in certain online polls recently, you’ve probably encountered a little test on the screen in the form of a block of warped, distorted and random letters or words. You have to type the matching letters or words you see in a box before the site will let you do what you want to do. [NOTE: For a visual example of what a “captcha” is, see the sidebar on page 69.]

Turns out there’s a term for these funky little boxes of text. They’re called CAPTCHAs, which stands for “Completely Automated Turing Test to Tell Computers and Humans Apart” (why it’s not CATTTTCAHA is a discussion for another day). (“Turing” refers to Dr. Alan Turing who, back in the 1940s, developed a standard test for declaring a machine function as artificial intelligence.)

The CAPTCHA test was developed by researchers at Carnegie Mellon University back in 2000 as an application for Yahoo, which wanted to prevent spammers from using...