Captcha Recognition and Robustness Measurement using Image Processing Techniques

Ramya T
2013 IOSR Journal of Computer Engineering  
The advances in web-based technology have revolutionized the way people communicate and share information, necessitating firm security measures. Network security prevents and monitors unauthorized access, misuse, modification, or denial of a computer network and network-accessible resources. A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a standard security mechanism for addressing undesirable or malicious Internet bot programs. CAPTCHA generates and
more » ... CHA generates and grades tests that are human solvable, but beyond the capabilities of current computer programs. Captcha prevents quality degradation of a system by automated software, protect systems that are vulnerable to e-mail spam and minimizes automated posting to blogs, forums and wikis. This paper carries out a systematic study of various Text-based Captchas and proposes the application of Forepart based prediction and Character-Adaptive Masking to break these captchas to evaluate their robustness. Captcha segmentation and recognition is based on Forepart prediction, necessity sufficiency matching and Character-adaptive masking. Different classes of captchas like simple captchas, Botdetect captchas & Google captchas are taken into consideration.
doi:10.9790/0661-1316772 fatcat:gkglexhyivhihkr26mhh6h2klu