This GCHQ report dated 3 February 2011 and written by a seconded NSA staff member, alludes to the agencies’ capabilities against 13 models of firewalls produced by Juniper Networks, Inc: see the Intercept article NSA Helped British Spies Find Security Holes In Juniper Firewalls, 23 December 2015.
This undated presentation from NSA’s Network Analysis Center describes agency techniques for overcoming Virtual Private Networks (VPNs): see the Der Spiegel story Prying Eyes: Inside the NSA’s War on Internet Security, 28 December 2014.
A series of casual posts written by a single author stationed in the NSA’s Signals Intelligence Directorate and posted on the agency’s intranet in 2012. Several posts written in December of that year describe the rationale and methodology of targeting systems administrators: see the Intercept article Inside the NSA’s Secret Efforts to Hunt and Hack System Administrators, 20 March 2014.
This extract from an NSA document dated December 2012 shows the agency’s concern that other nation-state actors are adopting similar techniques: see the Intercept article How the NSA Plans to Infect ‘Millions’ of Computers with Malware, 12 March 2014.
These pages from an NSA internal catalogue describe the tools available to the agency in 2008: see the Der Spiegel article NSA’s Secret Toolbox: Unit Offers Spy Gadgets for Every Need, 30 December 2013