Newspapers published the first in a series of reports based on classified documents describing United States and allied surveillance programmes, including the bulk collection of American telephone metadata under a secret court order.
Subsequent reporting described a programme granting intelligence agencies access to data held by large internet companies, and the interception of traffic on undersea fibre-optic cables. The source was later identified as Edward Snowden, a former contractor for the National Security Agency.
The disclosures prompted legislative change in the United States, diplomatic protests from allied governments and a rapid industry-wide move to encrypt internet traffic by default.
