Which federal agency is responsible for domestic intelligence and security?

The Department of Homeland Security (DHS) is primarily responsible for protecting the United States from a range of threats, including domestic intelligence and security matters. It was established in response to the September 11, 2001 terrorist attacks, and its mission includes preventing terrorist attacks, securing the nation's borders, and enhancing the security of the country's infrastructure.

While the FBI conducts intelligence and law enforcement operations related to domestic threats, its primary role is investigative and law enforcement-focused rather than broad intelligence. The Justice Department oversees the FBI but does not directly manage domestic intelligence efforts. The National Security Agency (NSA) is chiefly concerned with foreign intelligence and signals intelligence; thus, it does not have a primary role in domestic security operations. Therefore, the Department of Homeland Security serves as the central federal agency overseeing domestic intelligence and security initiatives, making it the correct answer in this context.