关键词: 验证码, 粘连字符, 分割, 卷积神经网络

Abstract: CAPTCHA has made great contributions on maintaining the Internet security and preventing malicious machine attack.However，through the existing pattern recognition techniques，some CAPTCHAs can also be recognized.This paper focuses on breaking mop and xicihutong web CAPTCHA with merged characters.The difficulty is the segmentation of merged characters in image.Aiming at mop CAPTCHA which has blur merged characters，the paper proposes a segmentation algorithm based on local teeny value and minimum projective value.As to xicihutong web CAPTCHA with interlaced merged characters，the color clustering is proposed by combining with the vertical projection to achieve the purpose of segmentation.It uses the convolution neural network to train and recognize them，reaching a high recognition rate.

Key words: Completely Automated Public Turing test to tell Computer and Humans Apart（CAPTCHA）, merged character, segmentation, convolutional neural network