Edward Snowden, a high school dropout turned computer whiz kid, has catapulted to worldwide fame as one of the most significant leakers of vast surveillance programs by the National Security Agency, one of the most secretive government agencies in the United States.

Snowden, 29, leaked classified documents because he believed the US government's surveillance powers had become so immense and intrusive that he felt compelled to denounce them, he said in an interview with Britain's Guardian newspaper.

"The public needs to decide whether these programs and policies are right or wrong," Snowden said in a video.

Snowden has since fled to Hong Kong, where he is seeking refuge from possible prosecution.

Computer skills

Snowdown acquired computer skills at a community college where he eventually received a general equivalency degree. He joined the Army Reserve in 2004 but lasted only four months after breaking both legs. He landed his first job with the NSA as a security guard before taking an information technology job with the Central Intelligence Agency in Geneva, Switzerland, in 2007. He left the CIA in 2009 to work for private contractors, including the US computer company Dell and the consultancy Booz Allen Hamilton. In his job with Booz Allen, he was assigned to NSA offices in Japan and later in Hawaii.

Booz Allen is a management and technology consulting firm located in Tysons Corner, Virginia. The company is majority owned by the private equity firm the Carlyle Group, once known for hiring former politicians as advisors, including former President George H.W. Bush and James A. Baker III, a former secretary of state.

Initially a provider of consulting services to a wide range of industries, Booz Allen derives nearly 98 percent of its revenue today from US government agencies. It has posted steady growth in recent years, including $219 million in net income on $5.8 billion in revenue in the business year that ended March 2013.

Booz Allen isn't the only company benefiting from the US government's sharply increased spending on high-tech intelligence gathering since the 9/11 terrorist attacks in the United States. Both the Bush and Obama administrations have chosen to rely heavily on private contractors.

The NSA, which is located in Fort Meade, Maryland, is an intelligence-gathering agency within the US Department of Defense. For many years, the government rarely acknowledged its existence, and its budget remains a secret. Essentially, the NSA eavesdrops on all foreign communications and encodes all US government communications.

Following the 9/11 attacks, President George W. Bush signed a secret executive order that authorized the NSA to conduct electronic surveillance of telephone and Internet communications within the US.

Prism

When the program was revealed in 2005, the administration defended it as essential to detecting communication patterns among possible terrorists. The program has continued under President Barack Obama.

Prism is the code name of a wide-ranging NSA surveillance program of Internet users that Snowden leaked. Several US high-tech giants, including Apple, Facebook, Google and Microsoft, have been linked to the program.