This undated GCHQ presentation describes some of the Question Focused Databases (QFDs) developed to analyse the massive amount of raw data the agency collects from undersea cables: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This GCHQ presentation from 23 March 2009 discusses the agency’s plan for “processing Events [metadata] at scale”: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This GCHQ briefing from September 2009 describes the tools then available to analyse metadata collected on a massive scale: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This page from GCHQ’s internal GCWiki describes the BLAZING SADDLES tool for handling huge amounts of metadata and the specialised analysis it supports: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This GCHQ research paper from 6 November 2009 outlines what kinds of data the agency can extract from internet radio stations and their listenership, grouped by country: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This undated page from GCHQ’s internal GCWiki shows that the agency’s usual retention periods for metadata and content can be extended for cyber defence purposes: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This GCHQ document from 18 August 2009 describes BLACK HOLE, a massive data repository, and describes how this interacts with other systems developed by the agency: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.