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AC-4(27) AC · Access Control

Redundant/Independent Filtering Mechanisms

LOW MODERATE HIGH
1 Overlay 0 Related Controls
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Requirements NIST SOURCE

When transferring information between different security domains, implement content filtering solutions that provide redundant and independent filtering mechanisms for each data type.

Discussion (NIST Supplemental Guidance)

Content filtering is the process of inspecting information as it traverses a cross-domain solution and determines if the information meets a predefined policy. Redundant and independent content filtering eliminates a single point of failure filtering system. Independence is defined as the implementation of a content filter that uses a different code base and supporting libraries (e.g., two JPEG filters using different vendors’ JPEG libraries) and multiple, independent system processes.

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 AC-4(27) 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. when transferring information between security domains, implemented content filtering solutions provide redundant and independent filtering mechanisms for each data type.

Examine

[SELECT FROM: Information flow enforcement policy; procedures addressing information flow enforcement; system design documentation; system configuration settings and associated documentation; system audit records; system security plan; other relevant documents or records].

Interview

[SELECT FROM: Organizational personnel with information flow enforcement responsibilities; system/network administrators; organizational personnel with information security responsibilities].

Test

[SELECT FROM: Mechanisms implementing information flow enforcement functions].

Overlays

Showing the OT/ICS overlay for the parent control AC-4 — see the AC-4(27) 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

Not applicable at this tier.

MODERATE

  • Base control: Included (matches standard baseline)

HIGH

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

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for AC-4(27). 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

  • Information flow enforcement policy
  • system security plan

Configuration

  • system design documentation
  • system configuration settings and associated documentation

Testing

  • Mechanisms implementing information flow enforcement functions

Other Records

  • procedures addressing information flow enforcement
  • system audit records
  • other relevant documents or records