Government agencies and private security companies in the U.S. have found a cost-effective way to engage in warrantless surveillance of individuals, groups and places: a pay-for-access web tool called Fog Reveal. The tool enables law enforcement officers to see “patterns of life” – where and when people work and live, with whom they associate and what places they visit. The tool’s maker, Fog Data Science, claims to have billions of data points from over 250 million U.S. mobile devices. Fog Reveal came to light when the Electronic Frontier Foundation (EFF), a nonprofit that advocates for online civil liberties, was investigating...