Fight Spam with Re-Captcha. And Digitize Books.

By rick • May 25th, 2008 • Category: Web

Re-Captcha has to be one of the most ingenius ideas to ever grace the internets. What I primarily use it for is hiding my email from spam-robots. Rather than putting my email address on my blog in plain view for spam-bots to see, I use Re-Captcha to hide it, like so:

Here’s my E-Mail.

How neato is that?

Re-Captcha also offers their service to stop comment spam. They offer plugins for Wordpress, Joomla, Drupal, Movable Type — basically all the major content management systems.

“I’ve seen Anti-Spam tools before. Why use this one?”

I’ll tell ya why. Each time a person types a captcha, it helps to digitize a book:

About 60 million CAPTCHAs are solved by humans around the world every day. In each case, roughly ten seconds of human time are being spent. Individually, that’s not a lot of time, but in aggregate these little puzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort? reCAPTCHA does exactly that by channeling the effort spent solving CAPTCHAs online into “reading” books.

Isn’t that ingenius?

Tags: captcha, spam

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One comment »

Ryan May 30th, 2008 4:15 am:
Seems like a lot of effort to go to for hiding your e-mail - I think there are encryption scripts that make it a little bit more fluid but still stop bots from grabbing it.

I’ve used the ReCaptcha plugin on a few sites now and generally it’s not bad. However, captcha’s are one of the easiest systems to beat for spambots, so not sure how effective it is, or will be as bots mature.

The digitizing books thing is intriguing. I tried to figure out what effect the average ReCaptcha user has on the process, but couldn’t piece it together from the paragraph you quoted. So, for anyone else that’s curious - here’s more info:

To archive human knowledge and to make information more accessible to the world, multiple projects are currently digitizing physical books that were written before the computer age. The book pages are being photographically scanned, and then, to make them searchable, transformed into text using “Optical Character Recognition” (OCR). The transformation into text is useful because scanning a book produces images, which are difficult to store on small devices, expensive to download, and cannot be searched. The problem is that OCR is not perfect.

reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.

But if a computer can’t read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here’s how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.

Neat stuff!