Security requirement
Terminate the network connection associated with a communications session at the end of the session or after [Organization-defined: time period] of inactivity.
Discussion
This requirement applies to internal and external networks. Terminating network connections associated with communications sessions includes deallocating TCP/IP addresses or port pairs at the operating system level or deallocating networking assignments at the application level if multiple application sessions are using a single network connection. Time periods of inactivity may be established by organizations and include time periods by type of network access or for specific network accesses.
Tailoring decisions required
Resolve these values through the governing organization’s approved tailoring and risk-management process before declaring the requirement implemented.
Implementation perspective
Treat Network Disconnect as a CUI protection outcome that must be reflected in the system boundary, documented implementation, operational behavior, and assessment evidence. Pay particular attention to secure architecture, boundary protection, communications security, cryptography, and isolation of CUI processing.
- Confirm the requirement is in scope for the CUI system components, services, users, and external connections being assessed.
- Resolve every organization-defined parameter through an approved governance and tailoring process.
- Map each clause of the requirement to an accountable owner, implementation mechanism, and evidence source.
- Verify that inherited and shared implementations are supported by current provider evidence and responsibility boundaries.
- Collect evidence during normal operation and review changes, exceptions, and deficiencies on a risk-based cadence.
Questions to ask
- Which CUI assets, data flows, users, and services are protected by this requirement?
- Which portions are implemented locally, inherited, shared, or not applicable, and what evidence supports that determination?
- Do the system security plan, deployed configuration, operating process, and assessment evidence tell the same story?
- What change, incident, or threshold should trigger reassessment?
Evidence and validation
- network and trust-boundary diagrams
- firewall and gateway configurations
- cryptographic configuration and key records
- segmentation and isolation test results
Common failure patterns
- diagrams omitting cloud and third-party paths
- encryption enabled without key governance
- flat trust zones permitting unnecessary lateral movement
- boundary rules accumulating without owner review
Assessment objectives and methods
Assessment objectives (1)
- SR-03.13.9.
the network connection associated with a communications session is terminated at the end of the session or after [Organization-defined: time period] of inactivity.
Examine
- system and communications protection policy and procedures
- procedures for network disconnect
- system design documentation
- system configuration settings
- system audit records
- system security plan
- other relevant documents or records
Interview
- personnel with information security responsibilities
- system developers
- system administrators
Test
- mechanisms for supporting or implementing a network disconnect capability
Source NIST SP 800-53 controls
These controls are referenced by the official SP 800-171 Rev. 3 OSCAL record. Open the corresponding control pages for complete control text, enhancements, D3FEND mappings, and related learning.
Authoritative sources
- NIST SP 800-171 Revision 3 official publication ↗
- NIST SP 800-171A Revision 3 official publication ↗
- NIST OSCAL Content release used for this import ↗
Bare Metal Cyber is an independent educational publisher and is not affiliated with or endorsed by NIST. The official publications, the responsible federal agency, and the governing contract or agreement determine applicability, tailoring, assessment depth, and required implementation.