Some of the web’s biggest destinations for watching videos have quietly started using automation to remove extremist content from their sites, according to two people familiar with the process. The move is a major step forward for internet companies that are eager to eradicate violent propaganda from their sites and are under pressure to do so from governments around the world as attacks by extremists proliferate, from Syria to Belgium and the United States.

YouTube and Facebook are among the sites deploying systems to block or rapidly take down Islamic State videos and other similar material, the sources said. The technology was originally developed to identify and remove copyright-protected content on video sites. It looks for “hashes,” a type of unique digital fingerprint that internet companies automatically assign to specific videos, allowing all content with matching fingerprints to be removed rapidly. READ MORE