While working for Booz Allen Hamilton, the technology consulting firm that contracted for the NSA, Snowden reportedly used his access as a system administrator to borrow the electronic identities of officials with higher security clearances via NSAnet, the agency's intranet. Snowden reportedly used the identities obtain 20,000 documents containing information on the agency's controversial programs
"Every day, they are learning how brilliant [Snowden] was,” an anonymous former intelligence official told NBC. "This is why you don’t hire brilliant people for jobs like this. You hire smart people. Brilliant people get you in trouble.”
http://www.huffingtonpost.com/2013/08/29/edward-snowden-impersonated-nsa_n_3837459.html