https://arstechnica.com/tech-policy/2022/07/dhs-bought-shocking-amount-of-warrantless-phone-tracking-data-aclu-says/

For years, people have wondered not if, but how much, the Department of Homeland Security accesses mobile location data to monitor US citizens. This week, the American Civil Liberties Union released thousands of heavily redacted pages of documents that provide a “glimpse” of how DHS agencies came to leverage “a shocking amount” of location data, apparently purchasing data without following proper protocols to ensure they had the authority to do so.

Documents were shared with the ACLU "over the course of the last year through a Freedom of Information Act (FOIA) lawsuit." Then Politico got access and released a report confirming that DHS contracted with two surveillance companies, Babel Street and Venntel, to scour hundreds of millions of cellphones from 2017 to 2019 and access “more than 336,000 location data points across North America.” The collection of emails, contracts, spreadsheets, and presentation slides provide evidence that “the Trump administration’s immigration enforcers used mobile location data to track people’s movements on a larger scale than previously known,” and the practice has continued under Biden due to a contract that didn’t expire until 2021.