You're probably thinking of PhotoDNA from Microsoft: https://en.wikipedia.org/wiki/PhotoDNA https://en.wikipedia.org/wiki/PhotoDNA Apparently many of the bigge

You're probably thinking of PhotoDNA from Microsoft: https://en.wikipedia.org/wiki/PhotoDNA https://en.wikipedia.org/wiki/PhotoDNA Apparently many of the biggest online services, including MS and Facebook, are using it to scan images uploaded by their users.