A security company called NuCaptcha is incorporating advertising into a video CAPTCHA system that is much harder for computers to break.

NuCaptcha does CAPTCHAs but with a twist: rather than a static box of text the system runs the text as a streaming banner within a video. The movement of the text throws off automated CAPTCHA-solving software. The text also does not have to be obscured as much, making it much easier for people to read and likely to keep users on the website.

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http://www.pcworld.com/businesscenter/article/208666/security_company_strengthens_captchas_with_video.html