Classification of Intelligence Services According to the Scope of Powers
Intelligence services are also classified according to the scope of powers into 1) the services "protecting what is theirs" and 2) services searching for protecting what is theirs.
The former is the domain of services that are generally called counter-intelligence services. Their task is protection and defence, i.e. protection against threats, risk prevention; they operate mostly in their own country. They focus on the internal situation in the state (internal security), protection of their own classified information and protected values and infrastructures. The most exact term for this type of services is a service with the main sphere of activity within the territory of its state.
The generally used term "counter-intelligence service" can be wrongly understood as a service with the main or even only task i.e. counter intelligence in terms of counter-espionage (activity aimed at foreign intelligence activity within its own country). This is not true, as today counter-espionage is only one part of its activity, which is even not the dominating one. These services obtain information about activities which can endanger the sovereignty, territorial integrity, national security, constitutional order, classified information and important economic and political interests of the state.
They focus on information about organized crime, terrorism (the intelligence activity is the ultimate weapon in the fight against terrorism), extremism and other threats. These services focus their defensive intelligence activity mainly on internal risks or foreign risks with impact on internal development or events. Hence they are called security services.
The second sphere of activity is the domain of services that are generally called foreign intelligence services. Their mission is "the offensive", i.e. finding out foreign intentions, interests and classified information; they operate especially in foreign countries and focus on threats but especially on the protection of interests of their own state. The most exact term for this type of services is a service with the main sphere of activity outside its country. The commonly used synonyms are intelligence services, spy services, espionage services and external services.
Source: Petr Zeman - lectures, trainings and public speeches