From The NY Times:
A military arm of the intelligence community buys commercially available databases containing location data from smartphone apps and searches it for Americans’ past movements without a warrant, according to an unclassified memo obtained by The New York Times.
Defense Intelligence Agency analysts have searched for the movements of Americans within a commercial database in five investigations over the past two and a half years, agency officials disclosed in a memo they wrote for Senator Ron Wyden, Democrat of Oregon.
The Defense Intelligence Agency appears to be mainly buying and using location data for investigations about foreigners abroad; one of its main missions is detecting threats to American forces stationed around the world.
But, the memo said, the unidentified broker or brokers from which the government buys bulk smartphone location data does not separate American and foreign users. The Defense Intelligence Agency instead processes the data as it arrives to filter those records which appear to be on domestic soil and puts them in a separate database.