48 CFR § 39.002 - Definitions.
As used in this part—
Modular contracting means use of one or more contracts to acquire information technology systems in successive, interoperable increments.
National security system means any telecommunications or information system operated by the United States Government, the function, operation, or use of which—
(1) Involves intelligence activities;
(2) Involves cryptologic activities related to national security;
(3) Involves command and control of military forces;
(4) Involves equipment that is an integral part of a weapon or weapons system; or
(5) Is critical to the direct fulfillment of military or intelligence missions. This does not include a system that is to be used for routine administrative and business applications, such as payroll, finance, logistics, and personnel management applications.