The kind of disinformation now known as fake news has tainted public discourse for centuries, even millennia. It’s been amplified in our digital age as a weapon of fearmongers, mob-baiters, election-meddlers to widen social fissures, undermine democracies and bolster authoritarian regimes. Companies such as Facebook, Twitter and Google are under pressure to take action. In one of the most high-profile cases yet, Twitter and Facebook announced in August that they had deleted hundreds of fake accounts run by China meant to undermine pro-democracy protests in Hong Kong.