The Federal Bureau of Investigation refers to the United States' lead agency involved in the investigation of terrorism (Federal Bureau of Investigation, 2009). The federal law defines terrorism as a crime committed by non-state and state actors in order to influence the actions of the government through coercion or intimidation. Undeniably, terrorists have conducted destructive attacks that have resulted in massive loss of both lives and properties. Recent terrorist attacks that have led to massive loss are the Westgate attack in Kenya, the 1998 bomb blast in the American Embassy in Nairobi, and 11 September attack in the United States of America. Despite the existence of a number of security agencies in the United States, FBI has emerged as the lead agency in the fight against terrorist attacks. In this paper, I intend to unfold the responsibilities of the Federal Bureau of Investigation as a unit of the Justice Department, analyze how civil liberties fit into the responsibilities of the FBI, and then eventually scrutinize some of the challenges the FBI has encountered. In addition, this thesis shall examine some of the controversial acts such as the Patriot Act, Foreign Intelligence Surveillance Act (FISA), and the Protect America Act.