Edward Snowden, a former US National Security Agency (NSA) contractor, now lives in Russia after fleeing the United States via Hong Kong in May, having revealed extensive internet and phone surveillance by US intelligence.
Journalists who interviewed him at his secret location in Hong Kong described him as "quiet, smart, easy-going and self-effacing. A master on computers".
Explaining why he decided to leave the US, he told the Guardian: "I don't want to live in a society that does these sort of things… I do not want to live in a world where everything I do and say is recorded."
The US has charged Mr Snowden with theft of government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence.
Each of the charges carries a maximum 10-year prison sentence.
Mr Snowden, 30, had been living with his girlfriend in Hawaii, but left, initially for Hong Kong where, with his consent, the UK's Guardian newspaper revealed his identity.
After the US filed charges and asked local authorities to extradite him, Mr Snowden left Hong Kong on 23 June, initially for Moscow, but with the intention of seeking asylum in Ecuador.
Ecuador has said it could not consider Mr Snowden's asylum request until he had arrived in the Latin American country, or one of its diplomatic missions.
With the knowledge that the US does have an extradition treaty with Hong Kong, Mr Snowden left on an Aeroflot flight to Moscow.
He remained in a transit zone in Moscow's Sheremetyevo airport for more than a month after the US revoked his travel documents. In August, he was given permission to enter Russia after he was offered asylum there for one year.
His father, Lon, visited him in October.
Mr Snowden is reported to have grown up in Elizabeth City, North Carolina, and later moved to Maryland, near the headquarters of the National Security Agency (NSA) at Fort Meade.
Describing himself as a less-than-stellar student, he is said to have studied computing at a Maryland community college to get the necessary credits to obtain a high school diploma. However, he never finished the course.
In 2003, he joined the US Army and began training with the special forces, only to be discharged after breaking both his legs in a training accident.
His first job with the NSA was as a security guard for one of the agency's secret facilities at the University of Maryland. He then worked on IT security at the Central Intelligence Agency (CIA).
Despite his lack of formal qualifications, it is said that his computer wizardry allowed him to quickly rise through intelligence ranks.
By 2007, he was given a CIA post with diplomatic cover in Geneva.
Mr Snowden told the Guardian: "Much of what I saw in Geneva really disillusioned me about how my government functions and what its impact is in the world. I realised that I was part of something that was doing far more harm than good."
Mr Snowden said he had considered going public earlier, but waited to see whether President Barack Obama's election in 2008 would change the US approach.
"[Mr Obama] continued with the policies of his predecessor," he said.
According to campaign finance records, Mr Snowden gave money in 2012 to Republican presidential long-shot Ron Paul, who supports strictly curtailing the powers of government.
Mr Snowden reportedly made two donations of $250 (£160) over the course of the campaign.
He left the CIA in 2009 and began working at the NSA as an employee of various outside contractors, including consulting giant Booz Allen.
In a statement, the company confirmed he had been an employee of the firm for less than three months, assigned to a team in Hawaii.
"News reports that this individual has claimed to have leaked classified information are shocking, and if accurate, this action represents a grave violation of the code of conduct and core values of our firm, it said.
Mr Snowden admitted to Hong Kong's South China Morning Post newspaper that he took the job at Booz Allen because he wanted access to classified information to gather evidence.
He was formally sacked on 11 June.
Mr Snowden was on a salary of $122,000 according to a statement from his employer.
He and his girlfriend moved out of their home in Waipahu, West Oahu, Hawaii, on 1 May, estate agents said, leaving nothing behind.
A neighbour told ABC that the couple usually kept the blinds and doors closed and "didn't really talk to anyone at all around here".
His then-girlfriend, whose personal blog includes photos of her pole dancing, has said her partner's sudden disappearance caught her by surprise.
"My world has opened and closed all at once," Lindsay Mills wrote. "Leaving me lost at sea without a compass."