Analysis of Naver CAPTCHA with Effective Segmentation

Abstract

CAPTCHA is an automated test to tell apart computers from human mainly for web services, and it has been evolved since the most naive form in which users are requested to input simple strings has been introduced. Though many types of CAPTCHAs have been proposed, text-based CAPTCHAs have been widely prevailed for user convenience. In this paper, we introduce new segmentation schemes and show an attack method to break the CAPTCHA of Naver that occupies more than 70% of the market share in search engine. The experimental results show that 938 trials out of 1000 have successfully analyzed, which implies that we cannot use the CAPTCHA anymore.