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SI-4(4) SI · System and Information Integrity

Inbound and Outbound Communications Traffic

LOW ✓ MODERATE ✓ HIGH
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Requirements NIST SOURCE

Discussion (NIST Supplemental Guidance)

Unusual or unauthorized activities or conditions related to system inbound and outbound communications traffic includes internal traffic that indicates the presence of malicious code or unauthorized use of legitimate code or credentials within organizational systems or propagating among system components, signaling to external systems, and the unauthorized exporting of information. Evidence of malicious code or unauthorized use of legitimate code or credentials is used to identify potentially compromised systems or system components.

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 SI-4(4) 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. the frequency at which to monitor inbound communications traffic for unusual or unauthorized activities or conditions is defined;
  2. unusual or unauthorized activities or conditions that are to be monitored in inbound communications traffic are defined;
  3. the frequency at which to monitor outbound communications traffic for unusual or unauthorized activities or conditions is defined;
  4. unusual or unauthorized activities or conditions that are to be monitored in outbound communications traffic are defined;
  5. criteria for unusual or unauthorized activities or conditions for inbound communications traffic are defined;
  6. criteria for unusual or unauthorized activities or conditions for outbound communications traffic are defined;
  7. inbound communications traffic is monitored <SI-04(04)_ODP[01] frequency> for <SI-04(04)_ODP[02] unusual or unauthorized activities or conditions>;
  8. outbound communications traffic is monitored <SI-04(04)_ODP[03] frequency> for <SI-04(04)_ODP[04] unusual or unauthorized activities or conditions>.

Examine

[SELECT FROM: System and information integrity policy; system and information integrity procedures; procedures addressing system monitoring tools and techniques; system design documentation; system monitoring tools and techniques documentation; system configuration settings and associated documentation; system protocols; system audit records; system security plan; other relevant documents or records].

Interview

[SELECT FROM: System/network administrators; organizational personnel with information security responsibilities; organizational personnel installing, configuring, and/or maintaining the system; organizational personnel responsible for monitoring the system; organizational personnel responsible for the intrusion detection system].

Test

[SELECT FROM: Organizational processes for intrusion detection and system monitoring; mechanisms supporting and/or implementing intrusion detection and system monitoring capabilities; mechanisms supporting and/or implementing the monitoring of inbound and outbound communications traffic].

Overlays

Showing the OT/ICS overlay for the parent control SI-4 — see the SI-4(4) 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)

MODERATE

  • Base control: Included (matches standard baseline)
  • Included: (2) (4) (5)

HIGH

  • Base control: Included (matches standard baseline)
  • Included: (2) (4) (5) (10) (12) (14) (20) (22)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for SI-4(4). 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 information integrity policy
  • system security plan

Configuration

  • system design documentation
  • system configuration settings and associated documentation

Testing

  • Organizational processes for intrusion detection and system monitoring
  • mechanisms supporting and/or implementing intrusion detection and system monitoring capabilities
  • mechanisms supporting and/or implementing the monitoring of inbound and outbound communications traffic

Other Records

  • system and information integrity procedures
  • procedures addressing system monitoring tools and techniques
  • system monitoring tools and techniques documentation
  • system protocols
  • system audit records
  • other relevant documents or records