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AC-20(1) AC · Access Control

Limits on Authorized Use

LOW ✓ MODERATE ✓ HIGH
1 Overlay 1 Related Control
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Requirements NIST SOURCE

Permit authorized individuals to use an external system to access the system or to process, store, or transmit organization-controlled information only after:

Discussion (NIST Supplemental 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.

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-20(1) 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. authorized individuals are permitted 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 (if applicable);
  2. authorized individuals are permitted to use an external system to access the system or to process, store, or transmit organization-controlled information only after retention of approved system connection or processing agreements with the organizational entity hosting the external system (if applicable).

Examine

[SELECT FROM: Access control policy; procedures addressing the use of external systems; system connection or processing agreements; account management documents; system security plan; other relevant documents or records].

Interview

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

Test

[SELECT FROM: Mechanisms implementing limits on use of external systems].

Overlays

Showing the OT/ICS overlay for the parent control AC-20 — see the AC-20(1) 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: (1) (2)

HIGH

  • Base control: Included (matches standard baseline)
  • Included: (1) (2)

STIGs & CCIs

No STIG checks or CCI mappings are currently loaded for AC-20(1). 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

  • Access control policy
  • system security plan

Testing

  • Mechanisms implementing limits on use of external systems

Other Records

  • procedures addressing the use of external systems
  • system connection or processing agreements
  • account management documents
  • other relevant documents or records