This GCHQ presentation dated 14 May 2012 describes the agency receiving “more than 50 billion events [metadata records] per day” and some of the tools available for analysing that mass of data: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.

This GCHQ presentation from November 2010 shows that the agency was logging 30 billion metadata records per day by that year: 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, last updated on 1 May 2012 documents progress in a variety of the agency’ projects: see Facing Data Deluge, Secret U.K. Spying Report Warned of Intelligence Failure, 7 June 2016.

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 dated 12 November 2010 discuss some of the agency’s attacks against iPhone handsets: see the Der Spiegel article The Digital Arms Race: NSA Preps America for Future Battle, 17 January 2015.

This undated page from GCHQ’s internal GCWiki provides a definition of “event”, the term the agency uses to refer to a metadata record, showing the variety of data collected: see the Intercept article Profiled: From Radio to Porn, British Spies Track Web Users’ Online Identities, 25 September 2015.