Re: Defeating CAPTCHA

[victor <victor () outblaze com>]

I was struck by the CAPTCHA issue a while back too, it happens to me 
that CAPTCHA reminded me of all these anti-piracy technique that have 
been developed over the past 2 decades.   Put this special data into 
that sector of the disc so pc-tools can't copy it or install this 
special cd checker to make sure the cd is not pirated.  We all know the 
result, finding a crack to all these protection is only a question of when.

I would say CAPTCHA is too a case of trying to fight intelligent with 
more intelligent. which is an endless loop with no true winner.   And so 
I wonder maybe a true solution to this abuser protection issue lies 
somewhere else.

I myself look at the setup this way, all these tool hacker uses depends 
on one thing to function, the question being presented as part of the 
signup/login procedure, because we must make the question presentable 
online and friendly enough for humand to process, it is bound to be 
possible to come up with some porgram to come up/brute force the answer.

So in another word, the existence of the question itself has made it 
possible for hacker to come up with software to defeat the protection.  
In a way, the solution has itself become the problem, so I am thinking 
maybe instead of trying to improve it.  We should look into eliminating it.

I can see some good example out there that is going into that 
direction.  Many online banking service are taking advantage of SMS, 
sending user a passkey where they have to use to login to the service.   
Or this implementation  pay pal has implemented, that debit user's 
credit card and ask user to use that sum as some form of passkey as one 
of the gentlemen here has pointed out.

These solution are very expensive compare to CAPTCHA but the direction 
seems to be more reliable and hack-profe.  If a better solution to 
CAPTCHA should be found, this maybe one direction you fellow might want 
to consider.

Tor.



robert () webappsec org wrote:

> This was linked off of slashdot (http://it.slashdot.org/article.pl?sid=05/08/24/1629213&tid=172&tid=95) 
> and explains some of the ways people are breaking CAPTCHA (http://en.wikipedia.org/wiki/Captcha) based systems.
>
> http://sam.zoy.org/pwntcha/
>
> - Robert
> robert_at_webappsec.org
> http://www.cgisecurity.com
>
>
>  


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                          Victor
                          Development Engineer
                          Outblaze Ltd
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