For at least the last five years, the Department of Homeland Security tracked the movements of millions of people using cellphone data. DHS tracked citizens and non-citizens, both inside and outside the country.

According to a report released Monday by the American Civil Liberties Union, DHS spent millions of dollars to buy the data from two companies but isn’t getting warrants to obtain the data.

The warrantless purchase of this bulk data was first reported by the Wall Street Journal in 2020. At the time, the ACLU called the practice a violation of an Americans’ right against illegal search and seizure and that DHS is essentially buying its way around the Fourth Amendment.

The ACLU submitted a FOIA request to DHS and sued the agency to respond to the request. Monday’s release is part of the first batch of documents the ACLU is making public in relation to the lawsuit.

The ACLU’s report revealed a slew of contracts between certain elements within DHS, like Immigration and Customs Enforcement and U.S. Customs and Border Patrol, and the companies Venntel and Babel Street to buy location data.

In a marketing brochure to DHS, Venntel said its software automatically compiles, processes and validates more than 15 billion daily location signals from more than 250 million mobile devices. Venntel explained the data allows “pattern of life analysis to identify persons of interest.”

Venntel described the data as “digital exhaust,” and that most users voluntarily share their location information through various apps. The ACLU countered the average person doesn’t know how many apps on their phone are tracking their location, and they certainly wouldn’t want that sensitive information sold to the government in bulk.

It’s not clear from the documents the ACLU released whether DHS used the data collected to arrest specific people. Venntel said it doesn’t store person-identifying information, but the ACLU asserted the only reason to collect this type of data is to identify and track people.