CA-3(2): Classified National Security System Connections

CA-3(2) requires you to strictly control and formally authorize any connection involving a Classified National Security System (CNSS), and to document the approval, boundary conditions, and security controls for that connection. Operationally, treat every CNSS connection as a high-risk interconnection: no connectivity without written authorization, defined interface safeguards, and retained evidence.

Key takeaways:

• Treat CNSS connections as exceptional interconnections that require explicit authorization and strict boundary controls.
• Build an approval workflow that produces auditable artifacts: interconnection agreements, diagrams, control inheritance, and monitoring evidence.
• Expect assessors to test that “what’s connected” matches diagrams, approvals, and technical enforcement at the boundary.

The ca-3(2): classified national security system connections requirement sits inside the NIST SP 800-53 “System Interconnections” control family and addresses a specific risk: uncontrolled or poorly governed connectivity involving classified national security systems. For a CCO, GRC lead, or security compliance owner, the fastest way to operationalize CA-3(2) is to treat it as an interconnection governance requirement with sharp edges: connectivity must be explicitly approved, technically constrained, and continuously knowable.

This requirement becomes urgent whenever your environment touches classified processing, interfaces with a government CNSS enclave, supports a classified program, or depends on third parties that provide network, hosting, managed security, or identity services that could create pathways into or out of classified boundaries. Even if your organization is not a federal agency, CA-3(2) commonly appears in contract-driven security baselines and assessment criteria for contractor-operated systems handling federal data. In practice, audit success depends less on policy language and more on proof: a complete interconnection inventory, documented approvals, enforceable boundary controls, and monitoring records that show the connection stays within approved parameters.

Regulatory text

Regulatory excerpt (as provided): “NIST SP 800-53 control CA-3.2.” ¹

What the operator must do (requirement-level interpretation): CA-3(2) is the enhancement focused on Classified National Security System Connections under CA-3 (System Interconnections). You need a controlled, formally authorized approach for any interconnection that involves a CNSS, including documented interface conditions, security requirements for the connection, and evidence that the implemented boundary controls match the authorization basis. ²

Plain-English interpretation

If a classified national security system is connected to anything else (another internal enclave, an external network, a partner environment, or a third party service), you must:

1. decide and document that the connection is allowed,
2. define exactly what is permitted across the boundary, and
3. enforce and monitor those limits with technical controls and operational oversight.

Think of CA-3(2) as: “No CNSS connectivity by accident, convenience, or ‘temporary’ exceptions.”

Who it applies to

Entity scope

• Federal information systems where CNSS connectivity exists or is proposed. ²
• Contractor-operated systems handling federal data where the applicable baseline includes NIST SP 800-53 and the architecture includes CNSS connections, shared services, or cross-domain dependencies. ²

Operational context (what triggers the requirement)

CA-3(2) becomes real when any of the following are true:

• A system boundary includes a classified enclave or interfaces with one.
• A shared service (identity, logging, vulnerability scanning, SIEM, ticketing, patching, remote admin) needs connectivity into or out of a CNSS boundary.
• A third party provides managed network/security/hosting services that introduce routing, remote access, or admin pathways that touch CNSS.
• A “one-time” data transfer turns into recurring connectivity (common in program execution).

What you actually need to do (step-by-step)

Use this as an operator runbook to stand up CA-3(2) quickly and make it assessable.

1) Establish ownership and an approval gate

• Assign a control owner (system security officer, ISSM/ISSO equivalent, or security engineering lead) plus a risk acceptance authority (authorizing official or delegated authority consistent with your governance model).
• Implement a hard gate: no routing, VPN, peering, cross-domain path, or admin tool connectivity involving CNSS without the gate producing an approval record.
• Include third party connection requests in the same workflow (managed service providers, telecoms, cloud operators, integrators).

Operator tip: The gate should be tied to change management so “approved connection” and “implemented connection” are not separate systems that drift.

2) Build and maintain a CNSS interconnection inventory

Create an inventory that is scoped specifically to CNSS-related connections:

• Connection name and unique ID
• Systems on both sides of the boundary (including third parties)
• Data types and classification impact
• Protocols/ports/services and directionality
• Auth mechanism (e.g., mutual TLS, PAM jump host, dedicated circuit)
• Control ownership (who manages firewall rules, crypto, identity)
• Approval status and expiration/recertification trigger

This inventory is what auditors use to pick samples. Keep it current or expect painful evidence scrambles.

3) Document the interconnection terms (security + operational)

For each CNSS interconnection, produce a written package that covers:

• Purpose and mission need
• Boundary diagram with trust zones
• Allowed flows (source/destination, ports, protocol, data handling rules)
• Security requirements at the boundary (filtering, encryption, authentication, session logging, malware inspection as applicable)
• Operational responsibilities: who patches what, who monitors what, who responds to incidents, who has admin access
• Termination conditions: how to disable the connection quickly if risk changes

This can be an Interconnection Security Agreement (ISA), Memorandum of Agreement, or equivalent artifact consistent with your program’s governance, but it must be written and reviewable.

4) Implement technical enforcement that matches the paper

Assessors will test whether the network and systems enforce what your documentation claims. Common enforcement points:

• Boundary firewalls/ACLs: explicit allow-lists, no “any/any,” no unmanaged temporary rules
• Remote administration: jump hosts, PAM, session recording, MFA where applicable
• Cryptographic protections for the link as required by your architecture and policies
• Segmentation controls: VLANs/VRFs, routing policy, deny-by-default across zones
• Monitoring: logs from boundary devices, alerting on rule changes, unexpected traffic, failed auth, anomalous sessions

5) Validate the connection before go-live (and after changes)

Before enabling a CNSS interconnection:

• Confirm diagrams and inventory match actual routing and firewall policy.
• Test that only approved flows work; verify denial for everything else.
• Confirm logging is generated, collected, and reviewable.

After any change:

• Re-validate the allowed flows and logging.
• Update the interconnection package and inventory.

6) Set an ongoing review cadence tied to real triggers

Even without prescribing a fixed interval, you need a repeatable mechanism to re-check CNSS connections based on:

• Architecture changes (new subnets, new identity provider, new monitoring tooling)
• Third party changes (MSP tool swap, new remote access method)
• Major incidents, new threats, or new program requirements
• Contract renewals or re-competes that alter responsibility boundaries

Where Daydream fits naturally: teams lose time chasing scattered evidence across network tickets, third party contracts, and system diagrams. Daydream helps by mapping CA-3(2) to a named owner, a repeatable procedure, and a recurring evidence list so your audit packet is assembled continuously, not at the end. ¹

Required evidence and artifacts to retain

Keep artifacts in an audit-ready package per interconnection, plus a roll-up index.

Core artifacts ¹:

• Approved interconnection request and decision record (who approved, scope, date)
• Interconnection agreement / security terms document
• Network and trust boundary diagram (current version)
• Allowed-flow specification (ports/protocols/directionality; can be table-based)
• Firewall/ACL configurations or configuration extracts demonstrating enforcement
• Crypto/auth configuration evidence (as applicable)
• Pre-production validation results (test plan + outcomes)
• Monitoring/logging evidence showing the connection is observed
• Change records for any modifications to the connection

Program-level artifacts:

• CNSS interconnection inventory
• Standard operating procedure for requesting/reviewing/terminating CNSS connections
• Role assignment (RACI) for approvals, implementation, monitoring, and incident response

Common exam/audit questions and hangups

Assessors and auditors tend to probe these points:

• “Show me your complete list of CNSS connections. How do you know it’s complete?”
• “Pick one connection. Show the authorization, diagram, allowed flows, and the actual firewall rules.”
• “Who can change boundary rules, and how do you detect unauthorized changes?”
• “How do you manage third party remote access into CNSS-related systems?”
• “If you had to disable this connection today, what is the kill switch and who executes it?”

Hangups that cause findings:

• Inventory exists, but it’s missing “non-obvious” paths (monitoring agents, admin tools, directory sync, time services).
• Documentation says “deny-by-default,” but configs include broad rules, legacy routes, or unmanaged exceptions.
• Approval records don’t match the current architecture after changes.

Frequent implementation mistakes and how to avoid them

1. Treating “temporary” connectivity as exempt.
   Fix: enforce the same approval gate for time-bound connections, and require an explicit termination date in the approval record.

2. Documenting at too high a level.
   Fix: add an allowed-flow table that a network engineer can implement and an assessor can test.

3. Ignoring third party operational realities.
   Fix: require third parties to provide boundary control evidence (rule excerpts, access method details, logging handoff) as a contractual deliverable for any CNSS-touching service.

4. Letting diagrams drift from reality.
   Fix: tie diagram updates to change management closure criteria for CNSS-related changes.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for CA-3(2), so you should treat this as an assessment-driven requirement rather than a case-law-driven one. The risk is still concrete: an undocumented or uncontrolled CNSS interconnection expands the attack surface, complicates incident response, and can drive authorization findings, contract noncompliance, or mission-impacting connectivity shutdowns if discovered late. ²

A practical 30/60/90-day execution plan

First 30 days (stabilize and stop surprises)

• Name the CA-3(2) owner and approval authority; publish a single intake channel for CNSS connection requests.
• Produce an initial CNSS interconnection inventory from firewall rulesets, network diagrams, and third party service lists.
• Freeze undocumented CNSS connectivity changes except break-glass with written approval.

Days 31–60 (document and align controls to reality)

• For each known connection, create the interconnection package: purpose, diagram, allowed flows, responsibilities.
• Reconcile paper vs. configuration: remove broad rules, formalize exceptions, and document compensating controls where removal is not immediately possible.
• Stand up monitoring validation: confirm boundary logs are collected and searchable; define who reviews alerts.

Days 61–90 (make it auditable and repeatable)

• Run an internal “mini-assessment”: sample a few connections end-to-end (authorization → diagram → rules → logs).
• Add CNSS interconnection review steps into change management and third party onboarding.
• Implement an evidence calendar and repository structure so each connection’s artifacts stay current.

Frequently Asked Questions

Does CA-3(2) apply if we have no classified systems, only CUI?

CA-3(2) is specific to Classified National Security System connections. If your environment is CUI-only with no CNSS interconnections, document the rationale and scope boundary, then focus on baseline CA-3 without the CNSS enhancement. ²

What counts as a “connection” for CA-3(2)?

Treat any routable network path, remote administration method, shared service integration, or third party managed access that crosses the CNSS boundary as a connection. If data or commands can cross the boundary, capture it in the interconnection inventory. ²

We use a managed service provider for monitoring. Is that a CNSS connection?

If the MSP’s tooling connects into CNSS systems or pulls telemetry out across the boundary, it is an interconnection that needs explicit authorization, defined allowed flows, and monitoring evidence. Require the MSP to provide boundary and access evidence as part of service delivery. ²

What evidence is most persuasive in an assessment?

Auditors respond to “closed loop” evidence: a written approval, a diagram and allowed-flow table, the implemented firewall/identity configuration that enforces it, and logs that show the connection is monitored. Missing any link in that chain usually creates findings. ²

Can we satisfy CA-3(2) with policy only?

No. Policy helps define the gate, but CA-3(2) is assessed through operational proof that interconnections are authorized and constrained in the live environment. Expect configuration and monitoring evidence requests. ²

How do we keep CA-3(2) evidence current without constant scramble?

Tie CNSS connection artifacts to change management closure and maintain a per-connection evidence folder with a standard checklist. Tools like Daydream help by mapping the requirement to a recurring evidence set and named owners so collection becomes routine instead of event-driven. ¹

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON

2. NIST SP 800-53 Rev. 5