Intelligence agencies can provide the following services for their national governments.
There is a distinction between "security intelligence" and "foreign intelligence". Security intelligence pertains to domestic threats, including terrorism and espionage. Foreign intelligence involves information collection relating to the political, or economic activities of foreign states.
Some agencies have been involved in assassination, arms trafficking, coups d'état, and the placement of misinformation propaganda and other covert and clandestine operations to support their own or their governments' interests.
Books
Journals
Szoldra, Paul (May 11, 2013). "These 17 Agencies Make Up The Most Sophisticated Spy Network In The World". Business Insider. http://www.businessinsider.com/17-agencies-of-the-us-intelligence-community-2013-5 ↩