Internal security Internal security , or IS , is the act of keeping peace within the border s of a sovereign state or other self - governing territories . generally by upholding the national law and defending against internal security threats . Responsibility for internal security may range from police to paramilitary forces , and in exceptional circumstances , the military itself . Threats to internal security . Threats to the general peace may range from low - level civil disorder , large scale violence , or even an armed insurgency . Threats to internal security may be directed at either the state ' s citizen s , or the organs and infrastructure of the state itself , and may range from petty crime , serious organised crime , political or industrial unrest , or even domestic terrorism . Foreign powers may also act as a threat to internal security , by either committing or sponsoring terrorism or rebellion , without actually declaring war . Forces and agencies . Governmental responsibility for internal security will generally rest with an interior ministry , as opposed to a defence ministry . Depending on the state , a state ' s internal security will be maintained by either the ordinary police or law enforcement agencies or more militarised police forces ( known as Gendarmerie or , literally , the Internal Troops . ) . Other specialised internal security agencies may exist to augment these main forces , such as border guards , special police units , or aspects of the state ' s List of intelligence agencies . In some states , internal security may be the primary responsibility of a secret police force . The level of authorised force used by agencies and forces responsible for maintaining internal security might range from unarmed police to fully armed paramilitary organisations , or employ some level of less - lethal weapon ry in between . For violent situations , internal security forces may contain some element of military type equipment such as non - military armored vehicles . Justice aspects . Depending on the organisation of the state , internal security forces may have jurisdiction on national or federal levels . As the concept of internal security refers to the entity of the state and its citizens , persons who are threats to internal security may be designated as an enemy of the state or enemy of the people . Persons detained by internal security forces may either be dealt with by the normal criminal justice system , or for more serious crimes against internal security such as treason , they may face special measures such as secret trial s . In times of extreme unrest , internal security actions may include measures such as internment ( detention without trial ) . Relationship with the military . 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 defence , except in times of extreme unrest or other state of emergency , short of civil war . Often , military involvement in internal security is explicitly prohibited , or is restricted to authorised military aid to the civil power as part of the principle of civilian control of the military . Military special forces units may in some cases be put under the temporary command of civilian powers , for special internal security situations such as counter terrorism operations .