How Google scans your Gmail for child porn | The Verge

More details on automated child porn detection tools

"Other companies have access to similar photo tagging technology, including Microsoft, whose PhotoDNA software can also detect flagged images of abuse. PhotoDNA can calculate a mathematical hash for an image of child sexual abuse that allows it to recognize photos automatically even if they have been altered. The tech is now used by both Twitter and Facebook, after Microsoft donated it to the NCMEC in 2009. Videos, too, have become the focus of such digital fingerprinting programs. Google has its own Video ID software for detecting footage of child sexual abuse, and British company Friend MTS donated its Expose F1 detection program to the International Centre for Missing & Exploited Children (ICMEC) earlier this year."

How Google scans your Gmail for child porn | The Verge