AC-20(1)—Use of External Systems | Limits on Authorized Use
IL4 Mod
IL4 High
IL5
IL6
>Control Description
Permit authorized individuals to use an external system to access the system or to process, store, or transmit organization-controlled information only after:
(a) 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
(b) Retention of approved system connection or processing agreements with the organizational entity hosting the external system.
>DoD Impact Level Requirements
No specific parameter values or requirements for this impact level.
>Discussion
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.
>Programmatic Queries
Beta
Related Services
AWS Organizations
IAM Identity Center
AWS RAM
CLI Commands
List external accounts with cross-account access
aws iam list-roles --query "Roles[?contains(AssumeRolePolicyDocument.Statement[0].Principal.AWS,'arn:aws:iam::')].{Name:RoleName,TrustedAccount:AssumeRolePolicyDocument}"List Resource Access Manager shares with external accounts
aws ram get-resource-shares --resource-owner SELF --query 'resourceShares[].{Name:name,Status:status,AllowExternal:allowExternalPrincipals}'List S3 buckets with external access policies
aws s3api list-buckets --query 'Buckets[].Name' | xargs -I {} aws s3api get-bucket-policy --bucket {}Check for cross-account trust relationships
aws iam list-roles --query "Roles[?contains(to_string(AssumeRolePolicyDocument),'sts:AssumeRole')].{Name:RoleName,Arn:Arn}">Related Controls
>Assessment Interview Topics
Questions assessors commonly ask
Process & Governance:
- •What formal policies and procedures govern the implementation of AC-20(1) (Limits On Authorized Use)?
- •Who are the designated roles responsible for implementing, maintaining, and monitoring AC-20(1)?
- •How frequently is the AC-20(1) policy reviewed and updated, and what triggers policy changes?
- •What training or awareness programs ensure personnel understand their responsibilities related to AC-20(1)?
Technical Implementation:
- •Describe the specific technical mechanisms or controls used to enforce AC-20(1) requirements.
- •What automated tools, systems, or technologies are deployed to implement AC-20(1)?
- •How is AC-20(1) integrated into your system architecture and overall security posture?
- •What configuration settings, parameters, or technical specifications enforce AC-20(1) requirements?
Evidence & Documentation:
- •What documentation demonstrates the complete implementation of AC-20(1)?
- •What audit logs, records, reports, or monitoring data validate AC-20(1) compliance?
- •Can you provide evidence of periodic reviews, assessments, or testing of AC-20(1) effectiveness?
- •What artifacts would you present during a FedRAMP assessment to demonstrate AC-20(1) compliance?
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