Stanford researchers say that captcha security codes, asking Internet sign-up users to repeat a string of letters to prove the users are human, can be thwarted, and they have successfully defeated captcha at big name sites such as Visa, CNN, and eBay as proof. In fact, they found that thirteen out of 15 high-profile sites were vulnerable to automated attacks.
via Stanford researchers outsmart captcha codes. The only two that came out unscathed, Google and ReCaptcha.