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SC-7(5) SC · System and Communications Protection

Deny by Default — Allow by Exception

LOW ✓ MODERATE ✓ HIGH
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Requirements NIST SOURCE

Deny network communications traffic by default and allow network communications traffic by exception [one of: at managed interfaces; for].

Discussion (NIST Supplemental Guidance)

Denying by default and allowing by exception applies to inbound and outbound network communications traffic. A deny-all, permit-by-exception network communications traffic policy ensures that only those system connections that are essential and approved are allowed. Deny by default, allow by exception also applies to a system that is connected to an external system.

Implementation Guidance

Engineering Interpretation

Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.

No engineering interpretation has been authored for SC-7(5) yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.

Assessment

NIST SP 800-53A REV 5.2.0

Assessment Objectives

  1. one or more of the following PARAMETER VALUES is/are selected: {at managed interfaces; for <SC-07(05)_ODP[02] systems>};
  2. systems for which network communications traffic is denied by default and network communications traffic is allowed by exception are defined (if selected).
  3. network communications traffic is denied by default <SC-07(05)_ODP[01] SELECTED PARAMETER VALUES>;
  4. network communications traffic is allowed by exception <SC-07(05)_ODP[01] SELECTED PARAMETER VALUES>.

Examine

[SELECT FROM: System and communications protection policy; procedures addressing boundary protection; system design documentation; system configuration settings and associated documentation; system audit records; system security plan; other relevant documents or records].

Interview

[SELECT FROM: System/network administrators; organizational personnel with information security responsibilities; system developer; organizational personnel with boundary protection responsibilities].

Test

[SELECT FROM: Mechanisms implementing traffic management at managed interfaces].

Overlays

Showing the OT/ICS overlay for the parent control SC-7 — see the SC-7(5) entries within each baseline below.

OT/ICS Overlay SP 800-82r3

NIST SP 800-82r3 Appendix F, Table 22. Blank baseline means the control/control enhancement is not selected in that initial OT baseline.

LOW

  • Base control: Included (matches standard baseline)
  • Added: (28) (29)

MODERATE

  • Base control: Included (matches standard baseline)
  • Included: (3) (4) (5) (7) (8)
  • Added: (18) (28) (29)

HIGH

  • Base control: Included (matches standard baseline)
  • Included: (3) (4) (5) (7) (8) (18) (21)
  • Added: (28) (29)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for SC-7(5). This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.

Learn more about STIG/CCI integration →

Evidence

Potential Evidence — Derived

Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.

Policy

  • System and communications protection policy
  • system security plan

Configuration

  • system design documentation
  • system configuration settings and associated documentation

Testing

  • Mechanisms implementing traffic management at managed interfaces

Other Records

  • procedures addressing boundary protection
  • system audit records
  • other relevant documents or records