The FORWARD project blog » CAPTCHA http://blogs.ict-forward.eu/forward blogging on emerging and future threats Wed, 21 Jul 2010 13:42:28 +0000 en hourly 1 http://wordpress.org/?v=3.0 A new effective attack against Google’s reCAPTCHA http://blogs.ict-forward.eu/forward/a-new-effective-attack-against-googles-recaptcha/ http://blogs.ict-forward.eu/forward/a-new-effective-attack-against-googles-recaptcha/#comments Thu, 17 Dec 2009 19:33:00 +0000 Thanasis Petsas http://blogs.ict-forward.eu/forward/?p=552 A new effective attack against Google’s CAPTCHA mechanisms was invented by a security researcher lately. The whole attack procedure is presented in a paper that was released on Saturday. The attack is based on OCR (Optical Character Recognition) techinques that used to evade Googles’ reCAPTCHA (CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart, for more information click here). reCAPTCHA is a recent security measure that Google uses so as to stop malicious scripts of doing important tasks without has been done first a specific authentication process. This process requires the sense of sight, that a computer script can’t have, so that optical puzzles can be solved first, in order to continue with the task execution.

As the Register informs, the success rate of this attack is very significant considering number and size of active botnets of the Internet. To be more specific, in the same article is mentioned what Jonathan Wilkins of iSEC Partners had said: “The method had a total success rate of 17.5 percent against reCAPTCHA. The rate is significant because of the wide use of botnets by spammers and other miscreants. Even a modest-sized network of 10,000 infected machines with a success rate of 0.01 percent would yield 10 successes every second. That could translate into 864,000 new accounts every day.”

The whole article can be found here.

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