The United Kingdom – United States of America Agreement (UKUSA, /juːkuːˈsɑː/ ew-koo-SAH)^[1][2] is a multilateral agreement for cooperation in signals intelligence between the United Kingdom, the United States, Canada, Australia, and New Zealand. The alliance of intelligence operations is also known as Five Eyes.^{[3][4][5][6][7]} In classification markings this is abbreviated as FVEY, with the individual countries being abbreviated as GBR, USA, CAN, AUS, and NZL respectively.^[8]

Emerging from an informal agreement related to the 1941 Atlantic Charter, the secret treaty was renewed with the passage of the 1943 BRUSA Agreement, before being officially enacted on 5 March 1946 by the United Kingdom and the United States. In the following years, it was extended to encompass Canada, Australia and New Zealand. Other countries, known as “third parties”, such as West Germany, the Philippines and several Nordic countries also joined the UKUSA community.^[9][10]

Much of the sharing of information is performed via the ultra-sensitive STONEGHOST network, which has been claimed to contain “some of the Western world’s most closely guarded secrets”.^[11] Besides laying down rules for intelligence sharing, the agreement formalized and cemented the “Special Relationship” between the UK and the USA.^[12][13]  

Due to its status as a secret treaty, its existence was not known to the Prime Minister of Australia until 1973,^[14] and it was not disclosed to the public until 2005.^[13] On 25 June 2010, for the first time in history, the full text of the agreement was publicly released by Britain and the United States, and can now be viewed online.^[9][15] Shortly after its release, the seven-page UKUSA Agreement was recognized by Time magazine as one of the Cold War‘s most important documents, with immense historical significance.^[13]

Currently, the global surveillance disclosure by Edward Snowden has shown that the intelligence-sharing activities between the First World allies of the Cold War are rapidly shifting into the digital realm of the Internet.^[16][17][18

The Five Eyes are cooperating with various 3rd Party countries in at least two groups:

• The “Nine Eyes”, consisting of the Five Eyes plus Denmark, France, the Netherlands and Norway.
• The “Fourteen Eyes”, consisting of the same countries as the Nine Eyes plus Germany, Belgium, Italy, Spain and Sweden.^[44] The actual name of this group is SIGINT Seniors Europe (SSEUR) and its purpose is coordinating the exchange of military signals intelligence among its members.^[45]

In 2013, Canadian federal judge Richard Mosley strongly rebuked the Canadian Security Intelligence Service (CSIS) for outsourcing its surveillance of Canadians to overseas partner agencies. A 51-page ruling says that the CSIS and other Canadian federal agencies are illegally enlisting U.S. and British allies in global surveillance dragnets, while keeping domestic federal courts in the dark.^[56][57][58]

NSA’s relationship with Canada’s CSEC                                                      

NSA document on a joint espionage operation with Canada’s CSEC agency during the G8 and G20 summits in Toronto in 2010