Lab interface added without review
A new reference lab VPN appears in production. CA-3 process would have required authorization, encryption standards, and an agreement before traffic carrying results/ePHI flowed.
System Interconnections
High Risk
Moderate
Low Cost
CA-3 requires authorizing connections from the system to other systems, documenting interface characteristics and security requirements, and reviewing/updating interconnection agreements on a defined frequency. HL7/FHIR links, HIE participation, payer portals, and BA integrations are interconnections that must be intentional — not shadow IT cables between networks.
Control Objective
Ensure every connection that can move ePHI between systems is authorized, documented, secured, and periodically reviewed.
Implementation Guidance
- Inventory all interconnections: interfaces, VPNs to partners, cloud peering, HIE, clearinghouses, and imaging exchanges.
- Record for each: parties, data types, direction, protocols, crypto, owners, and risk tier.
- Authorize new connections through change control and security review before go-live.
- Document agreements (ISA/MOU/BAA exhibits) with security requirements.
- Enforce technical controls at the boundary (AC-4/SC-7/SC-8).
- Review interconnections at least annually; disable unused ones.
- Monitor interface health and anomalous volumes.
- Include cloud-to-cloud and API partners — not only on-prem MLLP links.
Real-World Use Cases
How this control shows up in healthcare and HIPAA-covered environments.
HIE connection annual review
Yearly review finds an old data feed unused after a clinic closure; it is disabled and removed from diagrams.
BA analytics warehouse peering
Peering is limited to specific datasets with logging and an interconnection security agreement annexed to the BAA.
Best Practices
- Living interconnection inventory.
- Auth before connect.
- Written security requirements per link.
- Annual review and decommission unused links.
- Monitor volumes/anomalies.
- Align with BAAs and AC-4 flow diagrams.
Common Gaps & Violations
- Undocumented partner VPNs.
- Interfaces left online after projects end.
- No crypto requirements in agreements.
- Diagrams missing cloud API partners.
- Security review only after an incident.
Required Documentation
- Interconnection policy/procedure
- Interconnection inventory register
- ISA/MOU/BAA security exhibits
- Authorization/change tickets
- Periodic review records
How to Test & Validate
- Compare firewall partner rules to the interconnection register.
- Sample an interface for agreement + crypto evidence.
- Verify last review date.
- Confirm unused links are disabled.
- Trace a new connection through authorization workflow.
Audit Considerations
Assessors ask how partner connections are approved and secured. Undocumented ePHI interfaces are high-risk findings.
HIPAA Mapping
How this NIST control supports HIPAA Security Rule expectations.
- 164.308(b) Business Associate Contracts — many interconnections involve BAs requiring appropriate agreements.
- 164.312(e) Transmission Security — protect ePHI on interconnection paths.
- 164.308(a)(1) Risk Analysis — interconnections are key risk surfaces.
- 164.312(a) Access Control — limit which systems/users can use interconnection channels.
Compliance Tips
- Put CA-3 authorization on the interface go-live checklist.
- Reconcile interconnection register to firewall object-groups quarterly.
- Store diagrams next to BAA files for each partner.
Frequently Asked Questions
Is a patient portal an interconnection?
The portal system itself is your system; links from portal to EHR/payment processors/HIEs are interconnections to document under CA-3.
How does CA-3 relate to AC-4?
CA-3 authorizes/documents the connection relationship; AC-4 enforces information flow rules on those paths.
Do we need a formal ISA for every link?
Document security requirements appropriately — formal ISAs for higher-risk or government-style links; BAA exhibits and interface specs for many healthcare BA links.
References & Resources
- NIST SP 800-53 Rev. 5 — CA-3
- NIST SP 800-47 Interconnecting Systems
- Related controls: AC-4, SC-7, SC-8, SA-9
Related Guidelines
Related controls that commonly accompany CA-3.
Need Help Implementing CA-3?
Our auditors map NIST SP 800-53 controls to your HIPAA Security Rule program — policies, technical evidence, and audit readiness.