How did low-level contractor gain access to NSA programs?

(CBS News) WASHINGTON -- Edward Snowden was a foot soldier in an army of contractors doing top-secret work for the National Security Agency. He was assigned to an NSA installation in Hawaii, although his employer was the technology consulting firm Booz Allen Hamilton.

It is not unusual for contractors to have access to classified information. According to a report by the Director of National Intelligence, 483,000 contractors held top-secret clearances last year, compared to 791,000 government employees. Both go through the same background checks, a process which the report showed can take over a year.

What stunned officials about Snowden was that a low-level contractor could gain access to a number of disparate intelligence programs, each of them walled off behind levels of classification above his top-secret clearance.

Snowden's job was to ensure that classified computer networks were operating properly; that apparently allowed him to get past security barriers and browse at will.

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"I had access to, you know, the full rosters of everyone working at the NSA, the entire intelligence community and the entire undercover assets all around the world," Snowden said in an interview.

His employer, Booz Allen Hamilton, is well connected. One top executive there, Mike McConnell, is a former Director of National Intelligence. A former top executive there, James Clapper, is the current Director of National Intelligence.

Booz Allen Hamilton reported making $1.3 billion working for intelligence agencies last year, and it was not alone. A list of companies at a "Business in a Minute" conference hosted by the NSA includes household names like Boeing, IBM and General Dynamics.

There was explosive growth in top-secret contracting after 9/11 when intelligence agencies rapidly expanded their operations. You could call it the espionage-industrial complex, similar to the military-industrial complex President Eisenhower warned about more than 50 years ago.