This NSA classification guide, dated 21 November 2011, covers signals intelligence material that as to be kept secret for more than the standard 60 years: see the Der Spiegel article The NSA in Germany: Snowden’s Documents Available for Download, 18 June 2014.

This undated internal NSA document illustrates the degrees of cooperation in the agency’s relationships with different foreign powers. “Tier A” and “Tier B” are elsewhere referred to as Second and Third Parties: see the book No Place To Hide, 13 May 2014.

A brief description of a working group focused on monitoring and helping to exploit virtual private networks, or VPNs. Established in 2004, the working group publishes regular "VPN Target Activity Reports" on dozens of countries and organizations around the world. "These reports may help you exploit targets' VPNs more successfully," the chair of the working group writes.

In an interview, the deputy director describes his early days in the NSA's "weather shop," decrypting Soviet weather reports.

This 24 February 2005 article from the internal NSA newsletter Foreign Affairs Digest describes third party cooperation and interoperability in High Frequency Direction-Finding (HFDF): see the Intercept article Japan Made Secret Deals With The NSA That Expanded Global Surveillance, 24 April 2017.

A retiring colonel in the U.S. Air Force writes about his 30 years of service working in the world of signals intelligence for the military.

A joint US Navy and NSA report, prepared three months after a US spy plane was forced to crash land in China, assesses the degree to which surveillance secrets were compromised: see the Intercept article Burn After Reading: Snowden Documents Reveal Scope of Secrets Exposed to China in 2001 Spy Plane Incident, 10 April 2017. […]

This 2010 NSA presentation describes Project Camberdada, an attempt to subvert popular antivirus software by means of surveilling email traffic: see the Intercept article Popular Security Software Came Under Relentless NSA and GCHQ Attacks, 22 June 2015.

These July 2009 documents provide a full list of the fibre-optic cables GCHQ had access to at that point, including details of location, bandwidth and corporate partners: see the Süddeutsche Zeitung article Snowden-Leaks: How Vodafone-Subsidiary Cable & Wireless Aided GCHQ’s Spying Efforts, 25 November 2014. […]

This document lists the 193 governments, intragovernmental organisations and other entities which the NSA was granted the legal authority to intercept communications “about” for foreign intelligence purposes in August 2010: see the Washington Post article Court gave NSA broad leeway in surveillance, 30 June 2014.

An employee of the Cryptologic Applications Directorate writes about tours in Europe.

This NSA information paper from April 2013 describes the state of the agency’s intelligence relationship with its New Zealand counterpart: see the New Zealand Herald article NZ’s spy reach stretches across globe, 11 March 2015.

This slide, taken from the NSA’s annual review of its cooperation with foreign partners, shows an expansion in the agency’s international relationships: see the book No Place To Hide, 13 May 2014.

This joint GCHQ/MI6 presentation from February 2011 documents the process of international climate change negotiations becoming a “serious intelligence priority” for the UK: see the Dagbladet Information article Snowden documents reveal British climate espionage – Copenhagen climate summit targeted, 1 November 2014.  

The U.S. closed a number of High Frequency Direction-Finding sensor sites in the 1990s. To ensure they're able to track signals in areas that had previously been covered by now-shuttered stations, the Signals Intelligence Directorate worked with Second and Third Party partners to share resources and establish a global direction-finding network.