Move & Select: 2-Layer CAPTCHA Based on Cognitive Psychology for Securing Web Services
Moin Mahmud Tanvee, Mir Tafseer Nayeem · 2011
Nowadays, due to enormous growth of web users many services in the internet including Email, search engine, social networking are provided with free of charge. With the expansion of Web services, denial of service (DoS) attacks by malicious automated programs (e.g., web bots) is becoming a serious problem of web service accounts. CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a human authentication mechanism that generates and grades tests to determine whether the user is a human or a malicious computer program. These tests are easier for humans to solve and tough for automated bots. According to our study, the existing CAPTCHA techniques tried to maximize the difficulty for automated programs to pass tests by increasing distortion or noise. Consequently, it has also become difficult for humans too. In our proposed solution, we try to make use of human cognitive processing abilities into our CAPTCHA design. The suggested approach move and select is a 2-layer test, desired to improve security and reduce the solving time of human. In the result section we have studied both the usability and security issues of our design. The user studies indicate that this CAPTCHA can be solved with 99.04% average success rate in less than 10 seconds.