AC-4(27)_redundantindependent-filtering-mechanisms
DevOps & SecurityAC-4(27)_redundantindependent-filtering-mechanisms is an Agent Skill for devops & security published in the CyberStrikeus/CyberStrike repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.
When transferring information between different security domains, implement content filtering solutions that provide redundant and independent filteri
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AC-4(27) Redundant/Independent Filtering Mechanisms
Enhancement of: AC-4
High-Level Description
Family: Access Control (AC) Framework: NIST SP 800-53 Rev 5
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.
What to Check
- Verify AC-4(27) Redundant/Independent Filtering Mechanisms is documented in SSP
- Confirm control is operating effectively
- Review evidence of continuous monitoring for AC-4(27)
- Verify enhancement builds upon base control AC-4
How to Test
Step 1: Review Documentation
Examine the System Security Plan (SSP) and related artifacts for AC-4(27) implementation details. Verify the organization has documented how this control is satisfied.
Step 2: Validate Implementation
# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly
# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null
Step 3: Test Operating Effectiveness
Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.
Tools
| Tool | Purpose | Usage |
|---|---|---|
| cloud-audit-mcp | Check IAM policies and access controls | cloud_audit_iam_policies |
| hackbrowser-mcp | Test web application access controls | browser_auth_test |
Remediation Guide
Control Statement
When transferring information between different security domains, implement content filtering solutions that provide redundant and independent filtering mechanisms for each data type.
Implementation 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.
Risk Assessment
| Finding | Severity | Impact |
|---|---|---|
| AC-4(27) Redundant/Independent Filtering Mechanisms not implemented | High | Access Control |
| AC-4(27) partially implemented | Medium | Incomplete Access Control |
CWE Categories
| CWE ID | Title |
|---|---|
| CWE-284 | Improper Access Control |
References
- NIST SP 800-53 Rev 5 - AC-4(27)
- NIST SP 800-53A Rev 5 (Assessment Procedures)
- NIST SP 800-53 Rev 5 Full Catalog
Checklist
- Control documented in SSP
- Implementation evidence collected
- Operating effectiveness validated
- Continuous monitoring in place
- Related controls (none) reviewed