Local law enforcement agencies from suburban Southern California to rural North Carolina have been using an obscure cellphone tracking tool called “Fog Reveal,” at times without search warrants, that gives them the power to follow people’s movements months back in time, according to public records and internal emails obtained by The Associated Press.⁠ ⁠ The tool relies on advertising identification numbers, which Fog officials say are culled from popular cellphone apps such as Waze, Starbucks and hundreds of others that target ads based on a person’s movements and interests, according to police emails. That information is then sold to companies like Fog.⁠ ⁠ “It’s sort of a mass surveillance program on a budget,” said Bennett Cyphers, a special adviser at the Electronic Frontier Foundation, a digital privacy rights advocacy group.⁠ ⁠ Tap the link in bio to read the full investigation.