US department of Homeland Security (DHS) buys cellphone location data from private companies

Sidestepping the need to obtain a search warrant, the US Department of Homeland Security (DHS) has been accessing smartphone location data by buying it from private marketing that typically embed tracker in apps. This data, which maps the movement of millions of cellphones in America, was collected from ordinary cellphone apps, to which users gave access to their location. In this particular instance, it was used by the DHS to search for undocumented immigrants according to the Wall Street Journal. S
Contracting records show the federal government is buying the location data from Venntel, a small company that shares several executives and patents with Gravy Analytics, a major player in the mobile-advertising world. Venntel, in turn, purchased the information from private marketing companies that sell the location data of millions of cellphones to advertisers. Venntel is currently under investigation by the US Congress.
Source: https://www.wsj.com/articles/federal-agencies-use-cellphone-location-data-for-immigration-enforcement-11581078600
Write: Byron Tau & Michelle Hackman
Publication: The Wall Street Journal