CAPTCHA Cracking

CAPTCHAs are programs that generate images to test computers and humans in an effort to only let humans pass, a kind of reverse Turing test. (CAPTCHA stands for Completely Automated Public Turing Test To Tell Computers and Humans Apart.) A common type of CAPTCHA requires the user to type letters or digits from a distorted image that appears on the screen. Using image processing techniques one can often successfully beat visual CAPTCHAs by, for example, sharpening an image, adjusting, creating filters, or separating/subtracting colors. The sequence of images corresponds to the sequence of operators as displayed in the Manipulate from top to bottom. This Demonstration shows both image processing capabilities and optical character recognition (OCR) technology in Mathematica.