The ads on your phone aren't just selling you sneakers. They're a feed for anyone with a budget.

Tucson cops wanted to nail a suspected cigarette-store thief who had been hitting the same chain. So they pulled up the location pings of every phone near each robbery, noticed one device that kept showing up, and followed it home. That phone belonged to someone who was dating an employee at the store that was robbed first. Catching the guy would normally require a warrant, a wiretap, maybe a subpoena. It required a subscription.

The subscription, writes Joshua Villanueva at Lawfare , is to Webloc, an adtech-surveillance product whose owners claim it pulls data from roughly half a billion phones around the planet.…