A “confidential” program comes to light due to a public records request:
Hemisphere covers every call that passes through an AT&T switch — not just those made by AT&T customers — and includes calls dating back 26 years, according to Hemisphere training slides bearing the logo of the White House Office of National Drug Control Policy. Some four billion call records are added to the database every day, the slides say; technical specialists say a single call may generate more than one record. Unlike the N.S.A. data, the Hemisphere data includes information on the locations of callers.
Checks and balances:
Crucially, they said, the phone data is stored by AT&T, and not by the government as in the N.S.A. program. It is queried for phone numbers of interest mainly using what are called “administrative subpoenas,” those issued not by a grand jury or a judge but by a federal agency, in this case the D.E.A.
Here’s the whole presentation. The DEA concealed the existence of the Hemisphere program by using data from Hemisphere as a “pointer system” to make requests for full call records from suspects’ cell phone providers.
If you want a little more information on how law enforcement uses data from cell phones, this Ars Technica piece has a good run-down of how trawling through 150K cell numbers caught some bank robbers in the rural Southwest.