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03.13.09 Using CAPTCHA Images To Help Prevent Spam  By Dave Taylor My system administrator is telling me that I need to add a "capcha" [actually, it's "captcha"] system to my site so that I get less spam. What's a captcha system and why would I want it? Dave's Answer: Ah, spam, the bane of our collective online existence. It's a pain and it's frustrating how much time and effort we have to collectively expend trying to minimize its impact on our online experiences. Blech. Here's a fun fact that most people don't know: CAPTCHA is actually an acronym. It stands for "Completely Automated Public Turing test to tell Computers and Humans Apart." (Turing here refers to the brilliant computer scientist Alan Turing, who spent much time thinking about how to differentiate really smart computers from humans, to so-called "Turing test"). I know you've seen these. Here's a typical CAPTCHA from Google's site:  The basic idea is that it's some twisted or distorted or obfuscated text that you, as a human, will have no problem recognizing, but that a computer program would have a very tough time interpreting: if it can't figure out the words shown, it can't pretend to be a human and therefore can't spoof the system. Here's another example, from Craigslist:
 This one is more interesting in some sense because it's the same basic idea, but this recaptcha is actually also a distributed solution to interpreting difficult-to-read scanned text in old books being digitized. Nice win:win! Lots of sites use these, actually. Here's one from Facebook: Continue reading this article. About the Author: Dave Taylor is known as an expert on both business and technology issues. Holder of an MSEd and MBA, author of twenty books and founder of four startups, he also runs a marketing company and consults with firms seeking the best approach to working with weblogs and social networks. Dave is an award-winning speaker and frequent guest on radio and podcast programs. AskDaveTaylor.com http://www.intuitive.com/blog/ |
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