Counterintelligence is the business of identifying and dealing with foreign intelligence threats to a nation, such as the United States. Its main concern is the intelligence services of foreign states and similar organizations of non-state actors, such as transnational terrorist groups. Counterintelligence functions both as a defensive measure that protects the nation's secrets and assets against foreign intelligence penetration and as an offensive measure to find out what foreign intelligence organizations are planning to defeat better their aim. This article addresses the Federal Bureau of Investigation's (FBI) foreign counterintelligence function. It briefly traces its evolution by examining the key events and the issues that effected its growth as the principle civilian counterintelligence service of the U.S. government.
