“Leaker’s Security Check Faulted,” Wall Street Journal, August 28, 2013 A1, http://on.wsj.com/17j3vWb. Discussions of the cursory nature of the background check on Edward Snowden.
To protect sensitive information, one would normally segregate the information, limit access to trusted individuals, and monitor attempts by non-trusted individuals to access the information. And you would monitor and control downloads of that information by the trusted individuals.
One obvious failure in the Snowden case is how the government goes about figuring out who are trusted individuals. Especially someone with the high level of system access that Snowden had. But what about his ability to download information to three computers and a thumb drive? Apparently, no one (other than Snowden) knew about his downloads until he was in Hong Kong. And the Administration says the information downloaded was especially sensitive.
Compare and contrast Pfc. Bradley Manning.