Mostly, the tools of their trade are the keyboard and mouse - though, the most useful computer is the brain inside their heads.

"It's nothing like the movies," Australian Security Intelligence Organisation director-general Mike Burgess tells The Canberra Times.

"I'm living proof. I'm no Jason Bourne or Daniel Craig. There are lots of people - just normal people who work inside an organisation."

In the day-to-day reality, far from the film set, they are your neighbours and perhaps close friends - but always keeping the detail of their work back. You might have a suspicion but know not to push the question.

Spies, by definition, are secretive and unobtrusive, and Canberra is a city of spies.

The headquarters of the Australian Security Intelligence Organisation is a prominent landmark but a mystery. Everybody sees the Ben Chifley Buidling as they drive past on Parkes Way, but what goes on inside is an enigma.

But in the current exhibition, Spy: Espionage in Australia at the National Archives of Australia, we get a glimpse behind the curtain. Officers talk on video with their identity concealed - they are in silhouette with their voices distorted.

One of them - "Andrew" (he works in espionage so his identity may or may not be false) - describes his first days working for ASIO. "I thought everyone was tracking my movements and everywhere I went in the building I was being tracked and I was super nervous."

He kept wondering if he had done something wrong "so I would triple check my safe, my work station before I left for the day. It would often take me 15 minutes to leave".

Things most office workers take for granted are different at ASIO. "It's a weird sensation having the little things change [like] where you can't bring your phone to work. You can't tell your friends where you work."

Listening to the spies talking about their lives reveals that this ban on telling family and friends where they work isn't absolute. One officer, for example, says that on September 11, 2001, a close friend who knew where he worked called and told him to turn on the television.

They do tell family, but with great care and sparingly. "I never told the children where I worked until they were 18," another intelligence officer, "David", says.

When the spy did tell his family, the detail of daily life was still hidden. David wouldn't tell his wife about missions, "not to alarm her or the children but also to protect her because if something happened and they focused on her rather than me, she could be blissfully ignorant.''

He doesn't specify who "they" were but he joined the organisation (as the spies usually call it) after being badly wounded in Vietnam. For much of his career, the deadly Cold War cat-and-mouse has been his milieu.

He says the normal things the rest of us don't think twice about have to be addressed differently by an ASIO officer.

"If you go to the doctor, 'Where do you work?' [they ask]. It could be relevant to your health. What do you say? So if you do tell someone, you have to come back here and tell internal security, of which I was head officer for six years."

The Canberra commute is unusual - "Not driving the same way to work every day."

He plays a role. "It's like being in a play. You have to adopt the character, so I adopted the character of an ASIO officer, accepted that as my way of life ... and therefore performed the way one should as an actor performs on stage."

But having to deceive is draining. Academic studies have shown that people who deceive constantly die earlier. It puts a strain on a person's health.

Some do talk of a personal pressure. ASIO officers are trained in how to answer questions from friends and acquaintances. The technique seems to be to appear to say lots without saying much.

The director-general says it's not that different from lots of jobs. "Let's face it, in any organisation, there's actually quite a bit that you can talk about without going into the details, so you can be polite, civil and share a yarn."

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''Paul'' says that when he started with ASIO on January 5, 1987, "I certainly remember that first day feeling completely overloaded and overwhelmed with the information and the importance of protecting everything that you were seeing".

He adds, "I wasn't even sure that I could tell my dad what I had for lunch."

Why did Paul sign up? "I was a country boy growing up a couple of hours out of Canberra and, of course, there's no job prospects out in the bush unless you're on a farm, which I wasn't.

"So my big adventure was to move to Canberra and find a career there and, like most 19-year-olds, I didn't know what that career was going to be.

"I had undertaken the public service exam and rather than be accepted in the public service, I received a letter advising me that ASIO was relocating its headquarters from Melbourne to Canberra and they were interested in talking to me if I was interested in applying for a job there."

According to the latest annual report, ASIO has 1961 staff, though there is no breakdown between how many are in Canberra and how many are in the state capitals or elsewhere.

Not all the employees are "intelligence officers" - some are back-up clerical staff, lawyers and the like.

Spies is the popular name for the job, though in the trade they prefer the term "intelligence officers". Technically, not all "intelligence officers" may be spies in the sense that they monitor people either in the flesh and on the streets or online. Some analyse information.

And ASIO isn't the only institution involved in espionage. The Australian Secret Intelligence Service (ASIS) also gathers information, but abroad.

The budget for ASIO, the domestic agency, is $547 million. In the past year, the report says, there were 12,478 "counter-terrorism leads resolved or investigated", with three planned terrorist attacks disrupted.

The nature of its work shifted as the Cold War eventually gave way to the current age of terrorism.

As Andrew puts it, "Targets have moved away from the traditional telephone, meet down by the corner.

"Now, they're online using encrypted apps. It's not the old-school methods of passing a note on a street corner or a dead drop. It's online. It's obfuscating their activities. And that's making it more difficult for our techies as well."

The change has made their work more urgent. David describes the old Cold War world where the Soviet embassy might have a KGB agent he chooses to call Vladimir, on a three-year posting to Canberra. "You know everything about Vladimir. Everything.

"Three years is fine, but with terrorism sometimes you don't have three days. Sometimes you have three hours."

There was once a real Vladimir - Vladimir Petrov, who defected on April 3, 1954. ASIO had made contact with the Soviet spy and an Australian agent cultivated and befriended him. The Russian then sought asylum and money in exchange for Soviet intelligence.

Two armed Russian diplomatic staff then attempted to get his wife, Evdokia, out of Australia but were stopped on a stop-over in Darwin.

Since those Cold War days, there's been a gradual opening up of ASIO's business, a making of the case to the public who ultimately pay the bills - and that case is probably easier to make because of the visibility of the enemy and of the carnage the enemy can cause.

In the Cold War, the damage was through sensitive information the Soviet Union gained way behind the scenes. Today, the damage is there on the streets and in the pain caused to the victims of terrorism. It is in plain sight.

"Nobody cared if you went on television and said 'Guess what? We looked at Vladimir for three years'. Yawn. Nobody's going to die in Pitt Street from a bomb," is the way David puts it.

One of the big questions for the agency is how to balance its "intrusive powers" to investigate citizens with the right of citizens to privacy. If ASIO people don't probe enough and bad things happen, they get criticised but, on the other hand, innocent people demand privacy.

"That razor's edge most ASIO officers and managers and directors-general straddle every day," David says.

In the exhibition, there is surveillance film of communist party meetings. People going about their lawful business in a lawful organisation were monitored.

The argument for that surveillance was that to investigate an organisation hostile to Australia (as the Soviet Communist Party was) meant investigating associates of the Soviet Communist Party (as some Australian communists were).

Or so former ASIO director-general Duncan Lewis believes. "There were, of course, in this country large organisations that had been penetrated by the communist forces around the world and having undue influence.

"We were trying to protect our way of life. We were trying to protect our values."

He says there are "checks and balances that we are properly accountable".

"I am able to say that in the case of ASIO, we act lawfully in every respect and we are under enormous scrutiny - as we should be."

The interviews with spies (albeit those done and vetted by their employer) convey an intense commitment inside that building on Parkes Way.

Paul describes September 11, 2001, in Canberra. "I found myself watching it live on TV for a couple of hours and then I thought, even though the work that I was doing was not related at all to that threat, I thought I might go into work early.

"I found myself in bumper-to-bumper traffic on the way to Russell because it seemed that I wasn't the only one that had that idea, and at the old roundabout at Russell it was gridlock. It was everybody coming to work.

"A car park that normally didn't fill up until about 8.30 was completely full by 7.30. I found hundreds of colleagues just like me in the building with a sense of concern, with a sense of wanting to help and looking for an opportunity to contribute in some way."