According to AT&T’s explanation of these requests, the national security letters are subpoenas from the FBI regarding “counterterrorism or counterintelligence” that are limited to non-content information, like phone numbers dialed or information about the subscriber.
Because the law prohibits AT&T from providing a specific number on these requests, the company can only say that it received between 2,000 and 2,999 national security letters in 2013. These letters covered requests for between 4,000 and 4,999 accounts.
The FISA court orders are generally “related to national security investigations, such as international terrorism or espionage.” Data for these orders must be delayed by six months, so the latest info AT&T can share is from the first half of 2013.
While such orders can be for non-content requests, the AT&T data indicates that the requests related to the content of customers’ communications impacted a significantly larger number of accounts.
While non-content and content request each totaled between 0 and 999 between Jan. 1 and June 30, content-related requests involved somewhere between 35,000 and 35,999 accounts, while non-content orders only affected 0-999 accounts.
With regard to other law enforcement requests, AT&T says it received more than 301,000 criminal and civil litigation demands in 2013, with the largest chunk (223,000) being criminal subpoenas for customer information.
AT&T says it will be releasing these reports on a twice-annual basis.
Transparency Report [AT&T]