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reCAPTCHA: Thwarting Spammers - Digitizing Books!

CAPTCHA images are wonderful. I mean, well, not exactly. I guess, the simple fact that they make spam less horrible is what makes them so great. In a perfect world...there'd be no need. But it's done us a great service. But we shouldn't forget the disservice of the spammers. Every day people across the world spend 150,000 hours typing in CAPTCHA codes. In watts of computer time, that's around 9 megawatt hours a day. Not an insignificant amount!

Which is buy cheap generic viagra why Luis von Ahn, who pioneered the use of CAPTCHA with Yahoo!, has created a system to put those CAPTCHA codes to good use. Instead of just a random string of characters, von Ahn has created a system that pulls unreadable words from book digitization projects and uses them for CAPTCHA.

About 8% of words scanned from old books can't be directly digitized by optical character recognition software. So these words have to genuine viagra tablets from canada be filled in manually, an extremely time consuming process. But using von Ahn's new system the words difficult-to-read words get filled in by enterprising commenters and bulliten board posters.

Already the project, called "reCAPTCHA" has digitized over 2 million unrecognizable words through CAPTCHA inputs. Check out for more information. It's a brilliant idea...thwarting spammers while aiding the infinitely admirable act of cialis super active canada digitizing old books. Fantastic!

Via Technology Review
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Comments (22)Add Comment
Problems with reCAPTCHA
written by Adam, September 15, 2007
Hey, just so you know I had many problems with reCAPTACHA... Most of them related to you could enter in comments and not fill in the reCAPTCHA and still submit your comment.
Agreed, very annoying
written by Ted, September 15, 2007
I have trouble reading alot of CAPTCHA's, and I have perfect vision...there has to be a better way.
That's cool!
written by Live TV, September 16, 2007
I think it deserves some points and recognition for the fact that at least you know that your efforts are not in vain, you're actually contributing to something as opposed to just entering some random alphanumeric values that won't really do anything more meaningful besides posting your comment or verifying you're not a bot.
written by Mike, September 16, 2007
But if you don't know what the word is to start out with, couldn't you just type in any word and it would work?
I'm confused
written by Martang, September 16, 2007
Let me get this straight. A machine couldn't read these words. So now I'm supposed to shop viagra type the levitra dose unreadable words to verified by the machine that couldn't read them in the first place.
reCaptcha is difficult to use for many u
written by Eugenia, September 16, 2007
reCaptcha must make it easier to read these words. My readers emailed me with complaints when I added it to my blog a few weeks back.
written by Anthony, September 16, 2007
One of the words have already been identified correctly by the computer. Ex: "flirting" has been read correctly by the scanner, but "muscle" is unreadable. So if you identify "flirting" correctly, the server naturally assumes you've also read "muscles" (the unknown word) correctly.
Hmmmm. Doubtful...
written by Myztry, September 16, 2007
Getting the users to declare a word for an unreadable word (or any picture!) could work, by using the most common entry. The problem is initially the verification system would have no idea if it was wrong, and the spam BOTs might just end up getting the most votes if they use the cheap viagra pills same algorithm.
Also what happens if the image is truly unreadable (smudge / coffee spill / squashed fly)... Ironically a 10 cents an hour Chinese laborer would be more reliable at English deciphering.
written by Sean Gray, September 16, 2007
Most 10 cent an hour Chinese laborers can't read english.
written by Rob @, September 16, 2007
Captcha can filter most of the bot related spam ;)

Rob @
written by MMOnline, September 16, 2007
Oh! NO captcha can be detected by most of the bots/
written by Derrick, September 16, 2007
This is a novel idea indeed. Thanks for highlighting it! There must be an awful lot of sorting through the database of typed-in entries.
Interesting but...
written by nay min thu, September 16, 2007
Interesting... If the words can't be directly digitized by optical character recognition software, how does the system know whether or not what the user types in is correct?
My main point was...
written by Myztry, September 16, 2007
Even if the bots can't decipher the obscure text, there's every chance they'd get it consistently wrong (given same algorithm). Whereas human 'guesses' would vary thus spreading the 'votes'. Same problem if pictures were used. A BOT could just 'vote' for the CRC, and that would become correct. Whereas for a picture of a cougar, you could get 'cougar', 'panther', 'mountain lion', 'wild cat', etc, etc.
The human mind is buy pfizer viagra online a fantastic 'approximation' engine, but that hinders a 'learning program' such as a computer. If the Captcha software already knew the answer, it'd be a different story. But that defeats the viagra prices united states whole purpose!
You guys are retarded
written by Looser, September 16, 2007
Do you guys not think? The re-captcha offers up 2 different captcha words, one next to the other. One is from a book, and the other from a machine. Since you don't know which is which, you'll have to type both of them in correctly. The computer analyzes the one that's computer-generated to levitra 100 mg make sure it's correct. If it is, it will assume the other word is correct also.
written by Free Nature Photography Wallpaper, September 16, 2007
I get soo annoyed by these word verifications, I get them wrong half the time, and sometimes I can't even tell what it is... :( :(
Useful Information, but also not so usef
written by Keith, September 16, 2007
As we have all known that Captcha is used mainly to prevent bots for accessing and submitting information. As long as it works, I am not going to be too rigid on how it is being done.
written by ubuntu, September 16, 2007
This looks great!
i might add a capture in my website
written by money maker, September 16, 2007
i'm planning to add one in my website.

Mike from
This article has very useful information
written by Steve, September 20, 2007

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from Bangladesh

written by jg, February 05, 2010
CAPTCHA (1 control word) was ethical, reCAPTCHA (1 control word and 1 word they want you to translate for free) is not. there is nothing meaningful about it. Requiring two words takes longer (the have no significant research showing that it doesn't), and since we are translating past NYT archives, we are actually being exploited. I'd like to know who I should send an invoice to for my "work."

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