EvidenceSheet
FedRAMP High (NIST SP 800-53 Rev 5 baseline) · AC - Access Control

AC-20 Use of External Systems

Establish terms and conditions for use of external systems; prohibit unless authorized.

Source: FedRAMP High (NIST SP 800-53 Rev 5 baseline), AC-20. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open FedRAMP High (NIST SP 800-53 Rev 5 baseline) in the compliance library.

A FedRAMP baseline is a subset of NIST SP 800-53 Rev 5, enhancements included.

7
artefacts
1
held by a system
3
at each review
hard
to go live
Identity provider / directory
where the evidence lives
teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

  • Account provisioning and deprovisioning workflow tickets with manager approvals · Identity provider / directory

periodic reviewEvidence produced at each review

  • Signed terms and conditions or interconnection approvals for each permitted external system · Identity provider / directory
  • Joiner mover leaver workflow evidence integrated with HR · Identity provider / directory
  • Quarterly privileged access review attestations · Identity provider / directory

governing documentDocuments that govern the control

  • SSP AC-20 statement listing external systems users may reach (personal devices, partner tools) and the terms that allow or prohibit each · Policy repository / GRC workspace
  • Access control policy approved by the information security officer · Policy repository / GRC workspace
  • Role-based access matrix mapped to job functions and data classifications · Policy repository / GRC workspace

First move

Mostly documents and reviews. Pull the 1 system-held artefact from your Identity provider / directory on a schedule; put the documents under version control with an owner and review date, and log each review as a dated record with a named reviewer.

Common gaps auditors find

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

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AC-19(5) Full Device or Container-Based Encryption · AC-20(1) Limits on Authorized Use