The agency's mission is to strengthen Norway’s ability to counter espionage, sabotage, terrorism and hybrid threats. 

NSM helps organisations protect civilian and military information, systems, objects and infrastructure that are relevant to national security by giving advice and performing control activities, supervision, security testing and security research. In order to protect digital infrastructure, NSM operates a national warning system for critical infrastructure (VDI) and coordinates national efforts to handle serious cyberoperations. The National Cyber Security Centre (NCSC-NOR) is part of NSM. NSM is the governmental organisation authorised to approve cryptographic systems and products for the protection of information classified according to Norway’s Security Act.

NSM is administratively subordinate to the Ministry of Justice and Public Security. In addition, the Ministry of Defence has authority of NSM with respect to their area of responsibility.