The FBI has been conducting oversight of the NSA's email surveillance program, according to a declassified Justice Department report obtained by The New York Times, but details about how the bureau administered the program remain unclear. The 231-page study, obtained under a Freedom of Information Act lawsuit, reveals that the FBI began reviewing the NSA's PRISM program in 2008 and developed protocols to make sure that the email accounts it targeted belong to non-US citizens living overseas. In 2009, the bureau began gathering communications for its own purposes and began adding new email accounts and phone numbers to monitor through the NSA's upstream data collection program. Inspector General Michael Horowitz concludes in the study that the FBI was doing a good job limiting warrantless searches to non-American email accounts.

Documents leaked by former NSA contractor Edward Snowden have revealed much about the inner workings of the agency's surveillance programs, yet there remain questions over which agencies have access to the programs, and how they've been deployed. The Times report suggests that the FBI has access to the PRISM database and has broadened its own scope of surveillance, though there is still no indication that the program was limited to anti-terrorism or national security cases. The 2012 Justice Department study is at times heavily redacted, as well, with all but one reference to PRISM blacked out, despite the fact that the program has been publicly acknowledged. A lawyer for The New York Times says the paper may challenge those redactions at a later date.