“Venntel, a government contractor that sells location data of smartphones to U.S. law enforcement agencies including ICE, CBP, and the FBI, gathers information through a highly complex supply chain of advertising firms, data resellers, and ultimately innocuous-looking apps installed on peoples’ phones around the world, according to a cache of documents obtained by Norwegian media organization NRK and shared with Motherboard.”
Source : How an ICE Contractor Tracks Phones Around the World