SC-7(4)—External Telecommunications Services

a. Implement a managed interface for each external telecommunication service; b. Establish a traffic flow policy for each managed interface; c. Protect the confidentiality and integrity of the information being transmitted across each interface; d. Document each exception to the traffic flow policy with a supporting mission or business need and duration of that need; e. Review exceptions to the traffic flow policy [Assignment: organization-defined frequency] and remove exceptions that are no longer supported by an explicit mission or business need; f. Prevent unauthorized exchange of control plane traffic with external networks; g. Publish information to enable remote networks to detect unauthorized control plane traffic from internal networks; and h. Filter unauthorized control plane traffic from external networks.