Trump says he will be "very careful" to pardon Edward Snowden after calling him a "traitor".

Edward Snowden's book Permanent Record was published last year.

It offers by far the most comprehensive and personal account of how Snowden went from obscure NSA worker to whisker, sparking a national debate over the level of government surveillance by intelligence agencies desperate to avoid a repeat of the 9/11 attacks .

Intelligence officials who annually conduct classified damage assessments based on Snowden's statements have stated that the documents will remain publicly available for years to come.

Although the book appears six years after the revelations, Snowden, who fled first to Hong Kong and then to Russia, tries in his memoirs to place his concerns in a contemporary context.

"What is real is deliberately linked to what is fake through technologies capable of scaling that amalgamation into unprecedented global confusion," he says.

The story traces Snowden's development from childhood growing up in North Carolina and suburban Washington in the 1980s, where his mother worked for the NSA and his father served in the Coast Guard.

Growing up as the internet evolved from an obscure government computer network, he describes how a teenage fascination with technology – as a kid, took apart and reassembled a Nintendo console and hacked the Los Alamos nuclear lab network as a teenager – eventually led him to a career as an NSA contractor, where he watched high-tech espionage forces with increasing aversion.

Analysts used the government's collection powers to read and track emails of current and past lovers online, he writes.

A special program by the NSA called XKEYSCORE enabled the government to search the recent internet history of the average American.

He says he learned through this program that almost everyone who's been online has at least two things in common: they've all seen pornography at one time or another, and have saved all of their family's videos and pictures.

"That was true," he writes, "for virtually anyone, regardless of gender, ethnicity, race or age – from the meanest terrorist to the nicest senior who might be the grandparent or parent or cousin of the meanest terrorist."

He went out of his way to share his concerns with his girlfriend, who joined him in Russia and is now his wife.

“I couldn't tell her that my former NSA co-workers could target her for surveillance and read the love poems she wrote me. I couldn't tell her that they could access all of the photos she took – not just the public ones, but the intimate ones too, ”he writes.

"I couldn't tell her that her information was being collected, that all information was being collected, which amounted to a government threat: if you ever get out of line, we will use your private life against you."

Before summoning a small group of journalists to Hong Kong to divulge secret secrets, knowing that returning to the United States was impossible, he said he had prepared like a man about to die. He emptied his bank accounts, put cash in a steel ammunition box for his girlfriend, and erased and encrypted his old computers.

Today, he remains out of the reach of a US Department of Justice that filed charges of the Espionage Act just weeks after the revelations.

He spends much of his days behind a computer attending virtual meetings with fellow Freedom of the Press Foundation board members. "I shine on stages all over the world," he writes, to discuss civil liberties.

When he goes out, he tries to shake up his looks, sometimes with different glasses. He keeps his head down as he walks past buildings that are equipped with video surveillance equipment. Once, he says, he was recognized in a Moscow museum and agreed to a selfie request from a girl who spoke English with a German accent.

It is unclear when or if Snowden will return to a country where his family has deep roots. He traces his ancestry back to the Mayflower and the ancestors who fought in the War of Independence.

He was shaken by the 9/11 attacks, but describes his "reflexive, unquestionable support" for the wars that followed as the greatest regret of his life.

“It was as if the institutional policies I had developed had crashed – the anti-institutional hacking ethos instilled in me online and the apolitical patriotism I inherited from my parents were both erased from my system – and I was restarted as a willing means of revenge. & # 39;

He describes the 18 years since the 9/11 attacks as "a litany of American destruction through American self-destruction with the promulgation of secret policies, secret laws, secret courts and secret wars".

Reporting by Ross Ibbetson for MailOnline