National Security Letters have been around as long as the Internet, but only after the terrorist attacks of Sept. 11, 2001, have they been used with great frequency.
An NSL is a type of a subpoena issued by the Federal Bureau of Investigation that demands information from a customer's bank, telephone company, Internet service provider or email account. They are issued by an FBI agent and they don't require a court order.
What bothers most people about NSLs beyond the lack of a court order is that most come with a perpetual gag order that forbids the recipient from disclosing the existence of the letter. Recently, the gag orders and the letters themselves have been challenged in court on constitutional grounds. A number of cases that might have overturned the NSL practice were making their way through the federal courts when Congress passed the USA Freedom Act on June 2, 2015.
The act required that the FBI abandon the gag orders on NSLs three years after an investigation is resolved or when disclosure of an NSL's contents would not cause any harm to the investigation. At that point, the FBI is required to notify the recipient of an NSL that they can reveal both the existence and the contents.
Now Yahoo has become the first Internet services company to release an NSL's contents. Chris Madsen, head of global law enforcement, security and safety for Yahoo, revealed the contents of three NSLs in a blog posting on June 1, a year after the passage of the USA Freedom Act. Yahoo also notified two users that they were the subjects of an NSL inquiry the same time. The person connected to the third letter was not a Yahoo customer.
NSLs have been a source of irritation for the IT industry for years. Many companies felt that the letters were being misused, that the gag orders were unwarranted restrictions on their freedom and that there was insufficient oversight. While it was possible to challenge the NSL and its accompanying gag order in court, this happened only rarely.
The passage of the USA Freedom Act required the Department of Justice and the U.S. attorney general to develop procedures for dropping the gag orders and it also stiffened the requirements for issuing an NSL in the first place. Whether that resulted in a reduction in the number of NSLs issued by the FBI is unclear because, for the most part, the NSLs are still secret.
The three NSLs revealed by Yahoo are just the tip of the iceberg, coming as they are on the year after the passage of the act.