The robustness of a new CAPTCHA

  • Authors:
  • Ahmad Salah El Ahmad;Jeff Yan;Lindsay Marshall

  • Affiliations:
  • Newcastle University, UK;Newcastle University, UK;Newcastle University, UK

  • Venue:
  • Proceedings of the Third European Workshop on System Security
  • Year:
  • 2010

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Abstract

CAPTCHA is a standard security technology that presents tests to tell computers and humans apart. In this paper, we examine the security of a new CAPTCHA that was deployed until very recently by Megaupload, a leading online storage and delivery website. The security of this scheme relies on a novel segmentation resistance mechanism. However, we show that this CAPTCHA can be segmented using a simple but new automated attack with a success rate of 78%. It takes about 120 ms on average to segment each challenge on a standard desktop computer.