Last year, Edward Snowden downloaded tens of thousands of top-secret documents from a highly secure government computer network. The revelations that followed touched off a fierce debate over the massive surveillance operations conducted by the National Security Agency.
In the second part of "United States of Secrets," FRONTLINE explores the role of Silicon Valley in the National Security Agency's dragnet. As big technology companies encouraged users to share more and more information about their lives, they created a trove of data that could be useful not simply to advertisers, but also to the government.
Just two years in the job and armed with nuclear weapons, North Korea's Kim Jong-Un is the world's youngest dictator, ruling one of the world's most isolated countries. Like his father and grandfather, he wants to maintain tight control over what North Koreans see of the world -- and what the world sees of North Korea.