https://www.theverge.com/2018/5/23/17386972/facebook-revenge-porn-combat-uploading-hashing-nude-photos

Facebook made headlines last fall when news surfaced of a somewhat counterintuitive approach to combating revenge porn that involved asking users to upload nude photos to the company’s servers. Now, the official safety division of Facebook says it’s expanding that initial pilot program to the US, UK, and Canada. Previously, the solution had been deployed only in Australia and only in partnership with the office of the Australian government’s e-Safety Commissioner.

In a public post on the official Facebook Safety page, Global Head of Safety Antigone Davis says the company is “partnering with safety organizations on a way for people to securely submit photos they fear will be shared without their consent, so we can block them from being uploaded to Facebook, Instagram and Messenger.” Essentially, Facebook uses a technical approach known as hashing to tag sexually explicit photos that a user fears may be circulating without their consent. A hash is a numerical representation of a file that Facebook says cannot be read by humans, and the actual viewable image is then removed from the company’s servers once the hash is logged.