关键词: 验证码, 支持向量机（SVM）, 图像处理

Abstract: In order to verify the safety of the current CAPTCHA on the Internet banking, seven categories of representative CAPTCHAs of the current seven banks on the Internet are chosen to break. It presents an efficient method for solving visual textual CAPTCHAs using image processing techniques and SVM, such as graying, thresholding, interference noises removing, segmentation, character normalization, extracting feature vector for each character, and recognizing it based on SVM. It discusses defense from attacking viewpoint to improve the design of visual textual CAPTCHAs.

Key words: Completely Automated Public Test to tell Computers and Humans Apart（CAPTCHA）, Support Vector Machine（SVM）, image processing