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How robots and spiders are causing issues, how to stop them. We can also talk about Completely Automated Public Turing Test To Tell Computers And Humans Apart - their use, their compliance issues, porn proxies, PWNtcha and other ways to defeat them. 
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Google captcha spam
Posted by: Sandokan
Date: February 27, 2008 06:26PM

Anyone seen this? thoughts?
http://www.websense.com/securitylabs/blog/blog.php?BlogID=174

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Re: Google captcha spam
Posted by: Matt Presson
Date: February 28, 2008 03:25PM

Any CAPTCHA that uses characters to prove "humanness" will eventually be broken. It is only a matter of time until an OCR algorithm is tweaked to "reliably" identify the characters.

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Re: Google captcha spam
Posted by: Sandokan
Date: February 28, 2008 04:43PM

Yea, but they obviously have 2 code braking engines. I didn't even think of that, but what was written in the article, you could have several engines like this working together (not 2, like 10), as most engines that i have seen usually have troubles with this or that charachter, so you could have the engines send it all to 1 machine, and those chars that get hit the most, would usually be more correct. That could greatelly improve the rate of success. Most engines in applications i've seen so far had 1 captcha braking engine. It's an interesting concept really.
A "learning" engine could also be made from that, and improve the rate of success to 100% (theoretically).

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Re: Google captcha spam
Posted by: Malkav
Date: February 29, 2008 08:23AM

hmm

genetic evolution of captcha breaking...

typically a problem of fuzzy optimisation, ideally suited for genetic algorithms. encode your OCR parameters as a genoma, run iterations

breed top performers

randomize test

reiterate

yeah, character based turing test is dead. but that's just 'cause pattern recognition is not a Human property, but a complex aggregative system one
(obligatory heavyweight : http://www.amazon.com/Bright-Air-Brilliant-Fire-Matter/dp/0465007643)

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Those that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.
--Benjamin Franklin

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Re: Google captcha spam
Posted by: vizzy
Date: March 03, 2008 12:09PM

maybe my russian helps, but the translation on the blog is quite accurate, i wonder why nobody realize that this captcha breaking service is powered by e-mules! (aka humans).

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