AC-20(1)

Requirement
Permit authorized individuals to use an external system to access the system or to process, store, or transmit organization-controlled information only after:
1. 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
2. Retention of approved system connection or processing agreements with the organizational entity hosting the external system.

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.

NIST 800-53A Assessment Guidance

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].

ID	Assessment Objectives
AC-20(01)(a)	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 organizationís security and privacy policies and security and privacy plans (if applicable);
AC-20(01)(b)	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).

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