The term Big Brother is a common way to refer to an overly intrusive, controlling government. News that the FBI has been reading people's emails might make you say, "What else do you expect from Big Brother?"
You can use Big Brother when you talk about dictators and their authoritarian governments, or to describe abusive intrusions of more democratic governments into their citizens' privacy. The term comes from George Orwell's 1949 novel Nineteen Eighty-Four, in which Big Brother is the totalitarian leader of the book's fictional state. The people who live in this world are watched and controlled constantly by Big Brother, reminded frequently that "Big Brother is watching you."