Text-based CAPTCHA Strengths and Weaknesses

[Nytro]

Text-based CAPTCHA Strengths and Weaknesses

Elie Bursztein, Stanford University elie at cs.stanford.edu

Matthieu Martin, Stanford University mamartin at stanford.edu

John C. Mitchell jcm at cs.stanford.edu

The slides and paper are available from free from Text-based CAPTCHA Strengths and Weaknesses - Elie Bursztein

Follow Elie onTwitter : https://twitter.com/elie and Google+: http://ly.tl/g

ABSTRACT

We carry out a systematic study of existing visual CAPTCHAs based

on distorted characters that are augmented with anti-segmentation

techniques. Applying a systematic evaluation methodology to 15

current CAPTCHA schemes from popular web sites , we find that

13 are vulnerable to automated attacks. Based on this evaluation, we

identify a series of recommendations for CAPTCHA designers and

attackers, and possible future directions for producing more reliable

human/computer distinguishers.

Download:

http://cdn.ly.tl/publications/text-based-captcha-strengths-and-weaknesses.pdf