The scale and scope of the National Security Agency’s data collection operations certainly come as a shock when you see them presented as bluntly as they have been in recent days. So does the equally blunt attitude shown by US intelligence officials when they explain why they seemingly collected the telephone records of every single American. “Well, you have to start someplace,” Director of National Intelligence James Clapper reportedly told NBC News on Monday.

But what the NSA has been doing is, in a way, an extension of what it and its predecessor, the Armed Forces Security Agency, have been doing since the latter was founded in 1949 — and Australia has been an integral part of that the entire time through our Defence Signals Directorate.

English-speaking nations won World War II because we cracked the German and Japanese codes, or so goes the grand narrative that ignores 20 million Soviet deaths. Whatever. But immediately after the war the Soviets became the enemy, and soon after they got The Bomb.

The prospect of having your cities vaporised tends to focus the mind, so the five key English-speaking nations (the Five Eyes, they’re sometimes called) — the US, UK, Australia, Canada and New Zealand — formed an intelligence alliance to deal with the Soviet threat, and the Chinese, and others that came along during the Cold War and afterwards.

The core document of that alliance was, and still is, a secret treaty called the UKUSA Agreement, named after its first two signatory nations. It’s so secret that even the Australian prime minister didn’t know about it until 1973, or so it’s said.

UKUSA is about signals intelligence (SIGINT), a combination of the communications intelligence (COMINT) gathered from human communication and electronic intelligence (ELINT) from other stuff like radar systems and satellite telemetry.

Stated baldly, it’s the job of the Five Eyes’ SIGINT agencies to scoop up the world’s electronic communications — all of it, ideally, or as much as it can feasibly grab within technological, budgetary and other practical limitations — and analyse it looking for threats to national security. Each nation has its patch to monitor — Australia watches communications originating in Indochina, Indonesia, and southern China — but everything gets fed into the NSA’s vast analytical capabilities, from which member nations can obtain reports.

James Bamford’s definitive book about the NSA’s earlier history, The Puzzle Palace, says any communications between US citizens gathered by the agency was discarded, the identity of any US citizens in transcripts was redacted out, and posters and even banners in analysts’ work rooms reminded them of their legal responsibilities.

Australia had similar strong rules and strong indoctrination processes, I’m told by a former Cold Warrior who worked more in the directly military side of things. “People did take them seriously when I was in uniform, and there would be serious consequences if anyone broke the rules — although I’m personally unaware of any such cases,” he said.

The Cold Warrior says it would be difficult (though not impossible) for Australian spy agencies to target domestic citizens.

This global system was once code-named ECHELON, and that name is still used informally. ECHELON’s capabilities were obviously secret, but a 2001 report commissioned by the European Parliament provides a presumably accurate snapshot from that time.

Obviously such a vast surveillance capability, designed as it was to stop us all being fried in our sleep, also provides an excellent platform for monitoring citizens domestically. Such activities are banned under UKUSA, but as the agreement is secret, could it have been updated to allow domestic surveillance?

“That would mean significant changes to Australian law and the UKUSA agreement and a profound cultural change within the agencies themselves — to say nothing of the practical difficulties,” the Cold Warrior said.

But with all this secrecy, one does wonder if a phone call could be made for some informal domestic intelligence-gathering. How could we tell?