AC-21 — Information Sharing
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 us
Read the official statement, discussion, parameters, enhancements, and assessment methods →
NIST CSF 2.0 informative references
These CSF Subcategories list this base control or one of its enhancements in the imported NIST informative reference.
NIST SP 800-171 and SP 800-172
SP 800-171 requirements sourcing this control
SP 800-172 enhanced requirements sourcing this control
MITRE D3FEND techniques
MITRE ATT&CK relationships
Curated mitigation mappings
Inferred behavior relationships
Experimental: These relationships are inferred through D3FEND and must be validated against architecture, telemetry, and threat context.
Use the map without overclaiming.
A CSF informative reference is not an equivalence statement. A source-control relationship is not proof of implementation. A D3FEND semantic relationship is not a product claim. An inferred ATT&CK link is a hypothesis for engineering analysis.
Bare Metal Cyber is an independent educational publisher and is not affiliated with or endorsed by NIST or MITRE. Informative references and cross-framework relationships support navigation and analysis; they do not establish compliance, applicability, equivalence, control inheritance, or guaranteed mitigation effectiveness.