Attacking animated CAPTCHAs via character extraction

Authors

Vu Duc Nguyen, University of WollongongFollow
Yang-Wai Chow, University of WollongongFollow
Willy Susilo, University of WollongongFollow

RIS ID

74940

Publication Details

Nguyen, V., Chow, Y. & Susilo, W. (2012). Attacking animated CAPTCHAs via character extraction. Lecture Notes in Computer Science, 7712 (2012), 98-113.

Abstract

It is widely accepted that one of the principles in state-ofthe- art text-based CAPTCHA design, requires that a robust CAPTCHA scheme be segmentation-resistant. This paper establishes the fact that the segmentation-resistant principle does not only apply to traditional single image CAPTCHAs, but is very much relevant to the design of animated CAPTCHAs. In this paper, we show that animated CAPTCHAs not designed with this principle in mind can be easily be broken using simple techniques to extract individual characters from the animation frames. We present our experimental results on attacking 13 existing animated CAPTCHAs.