Take an inside look at a National Security Letter.

The silence has lifted.
Nicholas Merrill, founder of Calyx Internet Access, an Internet Service Provider, became the first person to challenge the overarching subpoena known as a National Security Letter when he filed a lawsuit against the order a decade ago. On Monday, he received permission to disclose the contents of the Federal Bureau of Investigation’s inquiry.
The letter—an investigatory tool that had been supercharged by the USA Patriot Act following the terror attacks of Sept. 11, 2001—requested that Merrill turn over any “electronic communication transactional record” associated with a particular customer’s account to the FBI.
A copy of the agency’s subpoena can be found here. It seeks information about the subscriber’s account, including email, physical mailing, and IP addresses as well as associated telephone numbers, screen names, dates of activity, and billing statements. The letter also solicits a “radius log,” which included location data derived from cell towers, the New York Times notes, citing a court opinion.
The FBI had barred Merrill from speaking about the letter when he first received it in 2004. Merrill filed his lawsuit anonymously as “John Doe” at the time.
In 2010, Merrill won the right to name himself as a recipient of the subpoena. After the government failed to appeal an August ruling within a 90-day deadline, Merrill earned the ability to speak publicly about the letter.
He chose not to reveal details about the target’s identity, citing “privacy reasons,” according to the Intercept.
Follow Robert Hackett on Twitter at @rhhackett. Read his cybersecurity, technology, and business coverage here. And subscribe to Data Sheet, Fortune’s daily newsletter on the business of technology, where he writes a weekly column.
For more about the FBI, watch the video below:
A crest of the Federal Bureau of Investigation is seen 03 August 2007 inside the J. Edgar Hoover FBI Building in Washington, DC. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)Mandel Ngan—AFP
 
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