AC-20(1)_limits-on-authorized-use
DevOps & SecurityAC-20(1)_limits-on-authorized-use 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.
Permit authorized individuals to use an external system to access the system or to process, store, or transmit organization-controlled information onl
How to use this skill
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Inspect the Agent Skill at https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/NIST/SP800-53_rev5/AC_access-control/AC-20(1)_limits-on-authorized-use/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/ac-20-1-limits-on-authorized-use, but wait for my approval before writing files or running scripts.
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AC-20(1) Limits on Authorized Use
Enhancement of: AC-20
High-Level Description
Family: Access Control (AC) Framework: NIST SP 800-53 Rev 5
Limiting authorized use recognizes circumstances where individuals using external systems may need to access organizational systems. Organizations need assurance that the external systems contain the necessary controls so as not to compromise, damage, or otherwise harm organizational systems. Verification that the required controls have been implemented can be achieved by external, independent assessments, attestations, or other means, depending on the confidence level required by organizations.
What to Check
- Verify AC-20(1) Limits on Authorized Use is documented in SSP
- Validate all 2 control requirements are implemented
- Confirm control is operating effectively
- Review evidence of continuous monitoring for AC-20(1)
- Verify enhancement builds upon base control AC-20
How to Test
Step 1: Review Documentation
Examine the System Security Plan (SSP) and related artifacts for AC-20(1) 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
Permit authorized individuals to use an external system to access the system or to process, store, or transmit organization-controlled information only after: Verification of the implementation of controls on the external system as specified in the organization’s security and privacy policies and security and privacy plans; or Retention of approved system connection or processing agreements with the organizational entity hosting the external system.
Implementation Guidance
Limiting authorized use recognizes circumstances where individuals using external systems may need to access organizational systems. Organizations need assurance that the external systems contain the necessary controls so as not to compromise, damage, or otherwise harm organizational systems. Verification that the required controls have been implemented can be achieved by external, independent assessments, attestations, or other means, depending on the confidence level required by organizations.
Risk Assessment
| Finding | Severity | Impact |
|---|---|---|
| AC-20(1) Limits on Authorized Use not implemented | High | Access Control |
| AC-20(1) partially implemented | Medium | Incomplete Access Control |
CWE Categories
| CWE ID | Title |
|---|---|
| CWE-284 | Improper Access Control |
References
- NIST SP 800-53 Rev 5 - AC-20(1)
- 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 (CA-2) reviewed