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.

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.

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.

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.

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.

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.

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.