iron curtain
1. (usually capitalized) The geographical border and military, political, and ideological barrier established and enforced by the Soviet Union that separated the countries of the Soviet bloc from the rest of Europe from 1945 to 1990. My great-grandfather used to live in East Germany before the Iron Curtain fell, back when the Soviet Union controlled every aspect of day-to-day life.
2. By extension, any barrier that excludes or prevents the free exchange of ideas, information, or communication from or between certain groups. Even though our company is a subsidiary, there seems to exist an iron curtain between our staff and the management of the larger corporation. For all our righteous calls for free speech and freedom of the press, it's important to remember that America had an iron curtain of its own during the Cold War, when even the slightest association with the Communist party was enough to get you blacklisted for life.