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May 29

Nikolaj Nyholm

Nikolaj Nyholm

reCaptcha - Stop Spam. Read Books.

Carnegie Mellon University professor Luis von Ahn's latest creation reCaptcha is yet another great example of bionic software on steroids.
You'll remember Luis von Ahn as the creator of ESP Game (licensed to Google as their Image Labeler) and derivative works Phetch and Peekaboom, but what is less known is that von Ahn is the person behind captchas, version 1.0.

reCaptcha makes captchas more useful than just preventing spam; by tapping into the reportedly 150.000 hours spent daily typing in captchas, reCaptcha has users proofread book text that OCR could not recognize and which would otherwise have to farmed out to a Mechanical Turk or other distributed proofreader.
Breaking up scanned text into small chunks for distributed processing by humans has been seen in various forms previously, including in banner ads (by inChorus, formerly Mycroft), but reCaptcha's ingeniousness lies in making an otherwise cumbersome task worthwhile every single time.

One can only speculate whether von Ahn have taken inspiration from ingenious spammers who were cracking captchas by asking users to solve captchas inlined from Hotmail and Y! mail in exchange for porn.
He who laughs last, laughs best. Will that be "Stop spam. Read books." or "Read Books. View Porn."?

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> You'll remember Luis von Ahn as the creator
> of ESP Game (licensed to Google as their
> Image Labeler)

Once again they reached out for Google's open source endeavours. See:

New tool screens spam, digitizes books

,----[ Quote ]
| A group of Carnegie Mellon University programmers has launched a
| service called ReCaptcha that can help cut down on spam while
| letting people digitize books.
| [...]
| The ReCaptcha service is available now through an application
| programming interface (API) for people to integrate into their
| Web sites. Software plug-ins to use the API are open-source
| software packages hosted at Google Code.

Nikolaj said:


Seems to me that they are just using Google Code to host the open source plugins for the reCaptcha. There is no indication that they're using any Google code in the project.


Mark said:

Lots of people have problems with spam, in their email, but web developers also have problems with people putting garbage into websites. I get a lot of comments from spammers who are trying to get links to their websites onto my blog. We get computer programs trying to win (by cheating) competitions we have created for our clients.

One of the solutions to that has always been the tedious email verification, login, password thing, which is too much if you just want someone to comment on your blog. Captcha is another solution, and I've just discovered (thanks to O'Reilly again for this) a brilliant spin on Captcha....


Oops, you're right. I didn't read it carefully at the time.

Does anyone else find this project hilarious. It is something like making the class-bully a monitor. When I say hilarious, I am not deriding the project. I hope that the project succeeds and creates a bigger book database than Project Gutenberg.

There is something to be said about 150.000 hours being wasted every day in filling image verification fields.

What we need now is for some way to capitalize on the 150.000 x 1000 number of hours people spend every day waiting for the page to load on slow connections.

kim said:

please remove the verification/puzzle word before sending my email because icannot guess any words posted.i refuse to use this captchas

Tracy Poff said:

Actually, one need not speculate on whether he was influenced by the spammers. He must have been.

He gave a talk on 26 July 2006 in which he explicitly mentions spammers using captchas for this.

The talk is available here:

hendra kuswoyo said:

why will join chat we must key in type the word...i know is good but we are time lost about wait brows that. thanks

diosadelfego said:

please remove the verification/puzzle word before sending my email because icannot guess any words posted.i refuse to use this captchas

J.O. Urban said:

Captchas can be so very annoying specially when they don't server a very useful purpose other then cutting down on spam posts. I wonder what other countless applications this reCaptcha v2.0 will have. Someone should start a reCaptcha Adnetwork where the network would pay publishers for every captcha ad viewed and submitted. Advertisers would have one more way to get in your face. Now Imagine that...

daniel- said:

pls stop capthca verification from my id

Custom said:

One thing is when people spend time in filling image verification fields, but there are so many sites where captcha working not correctly, or not working at all. So you can't see image thus and so you can't download something or post. This thing can spend not only your time, but your health too.

james said:

plz remove captcha from my id

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