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 GCHQ research report dated 20 September 2011, cowritten by researchers at Heilbronn Institute for Mathematical Research based at the University of Bristol, concerns the use of data mining techniques to develop usable intelligence as well as the contradictions that arise from the use of algorithms to identify wrong doers, or potential wrong doers. The paper also provides a great deal of background information on GCHQ operations and the detailed discussion of network theory demonstrates the power of metadata collection: see the Boing Boing article Doxxing Sherlock, 2 February 2016.
This page from GCHQ’s internal GCWiki provides a guide to the NSA’s XKeyScore tool: see the Der Spiegel article The NSA in Germany: Snowden’s Documents Available for Download, 18 June 2014.
This Boundless Informant slide shows the number of phone (DNR) and internet (DNI) records collected day-by-day between 10 December 2012 and 8 January 2013, from NSA’s foreign partners: see the Der Spiegel article Spying Together: Germany’s Deep Cooperation with the NSA, 18 June 2014.