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A Dispatch

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May 22, 2006

Captcha Gotcha

In Spam Wars I describe the background behind the Completely Automated Public Turing Test to Tell Computers and Humans Apart—CAPTCHA. These are the visual puzzles you sometimes get at Web sites where you either sign up for stuff or are requesting information that computerized robots would love to snarf. The purpose of the CAPTCHA is to make sure that a human, not an automated process, is actually filling out the form.

I've seen a lot of these, and sometimes I never know if I'm reading them correctly. The visual noise used to disguise the letters (to prevent optical character readers from trying to figure them out) is sometimes so intense, and sometimes the letters are so distorted, that I'll simply make a best guess at what I'm seeing.

That tactic failed the other day as I was entering an order at an online store. During the account creation phase, the site presented the following CAPTCHA challenge and I took a stab at what it read:

CAPTCHA screen shot

I believe my mistake was the "q," which may be a "g," even though the bottom of the letter is cut off. A tiny bit of the descender may be coming up from the bottom of the image. I'll never know, because like any good CAPTCHA usage, this site doesn't give you a second chance with the same image (I used the browser's Back button to get me to the page so I could grab the screenshot).

Now, I have pretty good (corrected) eyesight, and I like a good puzzle, which makes me wonder how those who have poorer eyesight and are puzzle-challenged fare with the increasingly noisy CAPTCHA challenges.

On the other hand, the site should have immediately known from my mistake that I was not a computer, for, as has been said: "To err is human."

Posted on May 22, 2006 at 08:12 AM