This 2010 NSA classication guide outlines the sensitivity of aspects of the agency’s hacking activities: see the Intercept article Core Secrets: NSA Saboteurs in China and Germany, 10 October 2010.
A June 2010 report from the NSA internal newsletter SIDtoday, authored by the chief of the agency’s Access and Target Development, describes the interdiction and backdooring of “shipments of computer network devices (servers, routers, etc.)”: see the book No Place To Hide, 13 May 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
A classification guide on the NSA’s Project BULLRUN goals and capabilities in decryption: see the Guardian article Revealed: how US and UK spy agencies defeat internet privacy and security, 5 September 2013.