Pixel Density Spam Filter
From the dawn of email, there has also been spam. And every time email providers seem to figure out a way to block it, spammers find a way around their new spam filters rather quickly. Bill Gates' prediction in 2006 that the end of spam was nigh proved to be somewhat premature, since users of typical email providers four years later are still relying on a good amount of common sense to block certain messages. Images have long been used by spammers as a way around spam filter defenses, but Yahoo has patented a new approach that offers spam detection in images.
Yahoo says that the technology works across any image type, even animated versions. The question is, how well does it work? Yahoo has not revealed specific numbers, but no matter how effective, it is unlikely to be a permanent solution to the problem. Once spammers figure out the metrics Yahoo is using to grade images, which are based on edge pixel distribution patterns, they can just find a way to alter their images to avoid detection.