The reCAPTCHA project is an attempt to make good use of the effort humans put into solving CAPTCHAs. In reCAPTCHA, a user is shown two distorted words, where one of the words is an actual CAPTCHA, but the other is a word – distorted to look like a CAPTCHA – that an optical character recognition (OCR) program was unable to recognize. If the real CAPTCHA is solved correctly, then the reCAPTCHA program assumes that the other word was also solved correctly. Since humans are good at correcting OCR errors, reCAPTCHA can be used, for example to improve the accuracy of digitized books
How could Trudy attack a reCAPTCHA system? That is, what could Trudy do to make the results obtained from a reCAPTCHA less reliable?