Bypassing Captcha By Machine A Proof For Passing The Turing Test
This addresses the problem of automated bot attacks on websites for web security, but it is incremental as it builds on existing OCR and CAPTCHA research.
The paper investigates the vulnerability of CAPTCHAs to machine attacks, showing that simple OCR can break some CAPTCHAs and advanced OCR can break more difficult ones, and proposes enhanced CAPTCHAs using characters, natural language, and multiple objects to resist such attacks.
For the last ten years, CAPTCHAs have been widely used by websites to prevent their data being automatically updated by machines. By supposedly allowing only humans to do so, CAPTCHAs take advantage of the reverse Turing test (TT), knowing that humans are more intelligent than machines. Generally, CAPTCHAs have defeated machines, but things are changing rapidly as technology improves. Hence, advanced research into optical character recognition (OCR) is overtaking attempts to strengthen CAPTCHAs against machine-based attacks. This paper investigates the immunity of CAPTCHA, which was built on the failure of the TT. We show that some CAPTCHAs are easily broken using a simple OCR machine built for the purpose of this study. By reviewing other techniques, we show that even more difficult CAPTCHAs can be broken using advanced OCR machines. Current advances in OCR should enable machines to pass the TT in the image recognition domain, which is exactly where machines are seeking to overcome CAPTCHAs. We enhance traditional CAPTCHAs by employing not only characters, but also natural language and multiple objects within the same CAPTCHA. The proposed CAPTCHAs might be able to hold out against machines, at least until the advent of a machine that passes the TT completely.