This page from GCHQ’s internal GCWiki, last edited in May 2012, provides background information on the agency’s “internet buffer business capability”: see the Der Spiegel article The NSA in Germany: Snowden’s Documents Available for Download, 18 June 2014.
This presentation gives an overview of the NSA’s programmes targeting the fibre optic cables that carry much of the world’s internet traffic. One slide gives a breakdown of which data sources form the basis of Presidential daily briefings. Another shows that the access point used to collect Yahoo and Google cloud data (MUSCULAR) is operated by GCHQ on UK territory. Slides detailing RAMPART cable accesses were published by the Intercept on 18 June 2014: see the Washington Post article How we know the NSA had access to internal Google and Yahoo cloud data, 4 November 2013.