FTA (emphasis mine): > The technology was first developed in 2009 by Microsoft, working closely with Dartmouth and the National Center for Missing and Exploite

FTA (emphasis mine): > The technology was first developed in 2009 by Microsoft, working closely with Dartmouth and the National Center for Missing and Exploited Children to clamp down on the same images of sexually abused children being circulated over and over again on the internet. There was technology that could find exact matches of images, but abusers could get around this by slightly altering the files – either by changing their size or adding a small mark. > PhotoDNA’s “hash” matching technology made it possible to identify known illegal images even if someone had altered them. Facebook, Twitter and Google all use the the same hash database to identify and remove illegal images.