Final answer:
FISMA defines 'National Security System' as a critical information system involving U.S. security operations, excluding routine administrative applications. The National Security Act established U.S. security structures like the CIA and NSA, with policies adapting over time to include various dimensions of security and counter diverse threats.
Step-by-step explanation:
The term “National Security System” as defined by the Federal Information Security Management Act (FISMA) pertains to a certain type of information system that is critical to the operations and assets of the United States. While FISMA itself is more broadly concerned with the protection and management of all federal information systems, national security systems specifically refer to those that involve intelligence activities, cryptologic activities related to national security, command and control of military forces, equipment integral to weapons or critical elements of defense, and other systems critical to the direct fulfillment of military or intelligence missions, not including routine administrative and business applications. The National Security Act also plays a crucial role in defining the structure and governance of the United States' security apparatus, including the creation of organizations like the CIA and the NSA, the implementation of security and surveillance programs, and the coordination and control of information pertinent to national defense and foreign policy.
Policies and measures taken to ensure national security have evolved greatly since the inception of the National Security Act of 1947. Over time, the scope has expanded beyond pure military strength to include economic, energy, and environmental security among other factors. The rise of non-state actors and unconventional threats has further complicated the landscape of national security, prompting the government to adopt diverse strategies ranging from civil defense to the enhancement of public safety through technology such as the Video Analyst System (VAS) and ensuring the resilience of the nation's critical infrastructure.