Threats to the general peace may range from minor civil unrest, large scale violence, or even an armed insurgency.
Foreign powers may also act as a threat to internal security, by either committing or sponsoring terrorism or rebellion, without actually declaring war.
For violent situations, internal security forces may contain some element of military type equipment such as non-military armored vehicles.
Depending on the organization of the state, internal security forces may have jurisdiction on national or federal levels.
Depending on the nature of the specific state's form of government, enforcing internal security will generally not be carried out by a country's military forces, whose primary role is external defense, except in times of extreme unrest or other state of emergency, short of civil war.