AC-21

Requirement
1. Enable authorized users to determine whether access authorizations assigned to a sharing partner match the information’s access and use restrictions for [Assignment: organization-defined information sharing circumstances where user discretion is required]; and
2. Employ [Assignment: organization-defined automated mechanisms or manual processes] to assist users in making information sharing and collaboration decisions.

Discussion

Information sharing applies to information that may be restricted in some manner based on some formal or administrative determination. Examples of such information include, contract-sensitive information, classified information related to special access programs or compartments, privileged information, proprietary information, and personally identifiable information. Security and privacy risk assessments as well as applicable laws, regulations, and policies can provide useful inputs to these determinations. Depending on the circumstances, sharing partners may be defined at the individual, group, or organizational level. Information may be defined by content, type, security category, or special access program or compartment. Access restrictions may include non-disclosure agreements (NDA). Information flow techniques and security attributes may be used to provide automated assistance to users making sharing and collaboration decisions.

NIST 800-53A Assessment Guidance

Examine

[SELECT FROM: Access control policy; procedures addressing user-based collaboration and information sharing (including restrictions); system design documentation; system configuration settings and associated documentation; list of users authorized to make information-sharing/collaboration decisions; list of information-sharing circumstances requiring user discretion; non-disclosure agreements; acquisitions/contractual agreements; system security plan; privacy plan; privacy impact assessment; security and privacy risk assessments; other relevant documents or records].

Interview

[SELECT FROM: Organizational personnel responsible for information-sharing/collaboration decisions; organizational personnel with responsibility for acquisitions/contractual agreements; system/network administrators; organizational personnel with information security and privacy responsibilities].

Test

[SELECT FROM: Automated mechanisms or manual process implementing access authorizations supporting information-sharing/user collaboration decisions].

ID	Assessment Objectives
AC-21a.	authorized users are enabled to determine whether access authorizations assigned to a sharing partner match the informationís access and use restrictions for <AC-21_ODP[01] information-sharing circumstances>;
AC-21b.	<AC-21_ODP[02] automated mechanisms> are employed to assist users in making information-sharing and collaboration decisions.

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