SC-3(1): Hardware Separation

SC-3(1): Hardware Separation requires you to isolate critical security functions using hardware-enforced boundaries, not just logical controls. To operationalize it quickly, identify which security functions must be isolated, select an approved hardware separation pattern (separate appliances, dedicated hosts, HSMs, or hardware-enforced partitions), implement it with documented configurations, and retain evidence that isolation is real and continuously maintained. ¹

Key takeaways:

• Hardware separation is about hardware-enforced isolation for security functions, not general segmentation. ¹
• Start by scoping “security functions” (e.g., key management, identity, audit) and mapping each to a concrete separation mechanism.
• Auditors look for repeatable evidence: architecture diagrams, build standards, configs, and verification test results tied to system boundaries.

The sc-3(1): hardware separation requirement is a narrow enhancement with a high practical payoff: it reduces the blast radius when an attacker compromises an application or a shared platform. The requirement is not asking you to buy new gear everywhere. It is asking you to make a deliberate choice that certain security functions deserve stronger isolation than software controls alone can provide, then prove that isolation exists in production and stays intact through change.

For most Compliance Officers, CCOs, and GRC leads, the fastest path is to translate the control into three decisions: (1) which security functions must be isolated for your system’s risk level, (2) what “hardware separation” means in your environment (dedicated hardware, hardware security modules, separate management plane hardware, or hardware-enforced partitions), and (3) what evidence you can produce on demand to show the boundary is hardware-backed and not merely a diagram.

This page gives requirement-level implementation guidance you can hand to infrastructure and security engineering, with the artifacts you need for assessment readiness under NIST SP 800-53 Rev. 5. ²

Regulatory text

Requirement (verbatim): “Employ hardware separation mechanisms to implement security function isolation.” ¹

What the operator must do: You must implement isolation for designated security functions using mechanisms that rely on hardware boundaries (or hardware-enforced separation) rather than only software controls. Then you must be able to demonstrate, with configurations and verification results, that the isolated security function cannot be modified, bypassed, or co-resident with less-trusted workloads in ways that break the intended boundary. ¹

Plain-English interpretation (what it really means)

SC-3(1) is about protecting security functions from the systems they protect. If the same host (or same general compute plane) runs both the business workload and the security control, a compromise of the workload can become a compromise of the control.

“Hardware separation” typically means one of these patterns:

• Dedicated physical device for the security function (e.g., separate logging collector, separate admin jump host hardware).
• Dedicated host(s) for the security function (no mixed workloads).
• Hardware security module (HSM) or dedicated key management hardware for cryptographic operations and key protection.
• Hardware-enforced partitions (where the isolation boundary is backed by CPU/virtualization hardware features and is governed as a hard boundary, with strong admin separation).

You do not need to isolate every component. You need to isolate the security functions you designate as requiring protection because their compromise would materially degrade security. ¹

Who it applies to (entity + operational context)

Applies to:

• Federal information systems implementing NIST SP 800-53 controls. ²
• Contractor systems handling federal data where NIST SP 800-53 is flowed down contractually or used as the governing control baseline. ²

Operational contexts where assessors most often expect SC-3(1) coverage:

• Systems hosting sensitive federal information types where compromise impact is high.
• Shared platforms where teams want to run security tooling “on the same cluster” as workloads.
• Environments with heavy automation where privileged pipelines can change security controls rapidly.

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

Use this as an implementation checklist you can assign and track.

Step 1: Define the “security functions” in scope

Create a short, explicit list for the system boundary. Common candidates:

• Key management and signing
• Identity and access enforcement components
• Security event collection and audit log integrity controls
• Policy enforcement points (network security gateways, host security enforcement)
• Admin access paths (jump hosts, out-of-band management)

Deliverable: Security Functions Inventory mapped to system components and owners.

Step 2: Choose an approved hardware separation pattern per function

Make it a governed design decision. For each in-scope function, record:

• Separation mechanism (dedicated hardware, dedicated host, HSM, hardware-enforced partition)
• Where it runs (data center, cloud account/project/subscription, isolated management environment)
• Trust boundary statement (what can and cannot share resources)

Deliverable: SC-3(1) Implementation Matrix (table format works best).

Example matrix fields (practical minimum):

• Security function
• Component(s)
• Separation mechanism
• Administrative domain (who can manage it)
• Evidence source (where configs/logs live)
• Change control gate (what prevents drift)

Step 3: Engineer the boundary so it survives “real life”

Hardware separation fails in practice when environments share privileged management or share build pipelines without controls.

Minimum engineering expectations to request:

• Separate administrative plane for the isolated security function (distinct privileged roles and MFA path).
• Controlled access to consoles/firmware/BMC/IPMI/iDRAC where applicable.
• Tight change control for images, templates, and infrastructure-as-code that creates the isolated component.
• Hardening baseline for the isolated device/host (CIS-style baselines are fine as internal standards, but document your own baseline).

Deliverable: Build Standard / Reference Architecture for separated security-function components.

Step 4: Implement verification tests (don’t rely on diagrams)

Auditors will ask how you know the separation is real. Build a simple verification approach:

• Attempted co-residency test: confirm non-security workloads cannot be scheduled/deployed onto the separated host/device class.
• Privilege boundary test: validate only approved admin roles can modify the security function configuration.
• Data path validation: confirm the security function’s critical secrets/keys cannot be exported from the separated mechanism (for HSMs/KMS designs, show policy and key attributes).

Deliverable: SC-3(1) Isolation Verification Procedure + latest test results.

Step 5: Operationalize drift detection and exception handling

You need a sustained control, not a one-time architecture.

Implement:

• Monitoring for configuration drift (host labels, cluster taints, IAM role changes, HSM policy changes).
• A formal exception process for temporary co-location or non-separated deployments, including risk acceptance and compensating controls.

Deliverable: Exception register entries (if any) plus periodic review notes.

Step 6: Map ownership, cadence, and evidence collection (assessment-ready)

A common failure mode is “implemented but unprovable.” Assign:

• Control owner (usually platform security or infrastructure)
• Evidence owner (often GRC collecting artifacts)
• Evidence cadence (e.g., per change, and periodic snapshots)
• Storage location (GRC repository, ticketing system, CMDB)

If you use Daydream, this is where it helps: map SC-3(1) to a single control record with named owners, an implementation procedure, and recurring evidence tasks so the artifacts stay current and assessor-ready. ¹

Required evidence and artifacts to retain

Keep evidence that proves (a) design intent, (b) implementation, and (c) continued operation.

Design evidence

• System boundary diagram showing where security functions live and which components are hardware-separated
• Security Functions Inventory (scoped list + rationale)
• SC-3(1) Implementation Matrix with separation mechanisms and owners

Build/config evidence

• Golden image or baseline configuration for dedicated hosts/devices
• HSM/KMS configuration exports or screenshots showing key non-exportability and admin controls (redact secrets)
• Infrastructure-as-code snippets establishing dedicated hosts, node pools, or isolated management environments (redact sensitive values)
• Role-based access control mappings for who can administer the separated security function

Operational evidence

• Latest isolation verification test results (dated, signed/approved)
• Change tickets for modifications to the separated components
• Drift detection alerts and closure notes (or periodic attestations)
• Exception register entries with approvals and compensating controls

Common exam/audit questions and hangups

Expect these questions from assessors and internal audit:

1. “Which security functions did you isolate, and why these?”
   Hangup: teams say “everything is isolated by VLAN.” SC-3(1) asks for hardware separation mechanisms. ¹

2. “Show me the hardware-enforced boundary.”
   Hangup: providing only architecture diagrams. You need configs, deployment constraints, and test results.

3. “Can an app admin become a security admin?”
   Hangup: shared admin roles, shared break-glass accounts, or shared CI/CD roles that can alter security controls.

4. “What stops co-resident workloads?”
   Hangup: “policy says don’t.” Assessors want enforcement: dedicated hosts, enforced scheduling constraints, and IAM separation.

5. “How do you keep this true after changes?”
   Hangup: no drift detection and no evidence cadence.

Frequent implementation mistakes (and how to avoid them)

Mistake	Why it fails SC-3(1)	What to do instead
Treating network segmentation as “hardware separation”	Segmentation can be bypassed if the host/control plane is compromised; SC-3(1) asks for hardware separation mechanisms. 1	Use dedicated devices/hosts, HSMs, or hardware-backed partitions for the security function.
Running security tooling on the same shared cluster “for convenience”	Breaks isolation if cluster admins or workloads can influence the security function	Stand up a dedicated node pool/host class with strict admin separation and deployment enforcement.
No clear definition of “security function”	Scope creep or under-scope; hard to defend decisions	Maintain a scoped list with rationale tied to impact if compromised.
Evidence lives in engineer heads	Fails audits even if technically correct	Store diagrams, configs, tests, and change records in a controlled repository and tie them to the control record (Daydream or your GRC system).
Exceptions become permanent	Risk acceptance without re-evaluation	Require expiry dates, compensating controls, and periodic re-approval for exceptions.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so this page does not cite enforcement outcomes.

Risk-wise, SC-3(1) reduces the chance that compromise of general compute or admin tooling leads to compromise of the security controls themselves. The operational implication: you will carry additional cost and complexity for separated components, so you should apply it to the security functions where loss of integrity or confidentiality would significantly weaken the system’s security posture. ¹

Practical 30/60/90-day execution plan

Use a concrete plan, but treat timing as adjustable based on system complexity and procurement cycles.

First 30 days (scope + design decisions)

• Name a control owner and evidence owner for SC-3(1).
• Build the Security Functions Inventory for the system boundary.
• Draft the SC-3(1) Implementation Matrix and get sign-off from security architecture.
• Identify gaps where current designs rely only on logical separation.

Days 31–60 (implement priority separations + evidence)

• Implement hardware separation for the highest-impact security function first (commonly key management or admin access path).
• Publish build standards/reference architecture for separated components.
• Stand up evidence collection: configs, diagrams, and change tickets in a single repository.
• Write and run the first isolation verification test; fix failures.

Days 61–90 (operationalize and make it durable)

• Add drift detection controls and alerting tied to the separated components.
• Formalize the exception process with approval workflow and compensating controls.
• Run a tabletop audit: have someone not on the engineering team answer the common audit questions using only retained evidence.
• If you run Daydream, convert the matrix into recurring evidence tasks so collection is automatic and consistent with the procedure. ¹

Frequently Asked Questions

Does virtualization or container isolation count as “hardware separation” for SC-3(1)?

It can, but only if you can show the isolation boundary is hardware-enforced and governed as a hard boundary for the security function. Be ready to produce configs and verification results that prove co-resident workloads and unauthorized admins cannot cross the boundary. ¹

Which security functions should I isolate first?

Start with the functions that, if compromised, let an attacker disable detection, change access rules, or steal keys. Key management, admin access paths, and audit/log integrity are common first picks, but scope should match your system risk and boundary. ¹

What evidence is usually most persuasive to an assessor?

Configuration and deployment constraints that enforce separation, plus a repeatable verification test with dated results. Diagrams help, but they rarely pass on their own.

We use a cloud provider. Do we need dedicated physical servers?

Not necessarily. The requirement is to employ hardware separation mechanisms for security function isolation; in cloud, that often means dedicated host constructs, isolated management environments, and hardware-backed key protection where applicable, supported by clear evidence. ¹

How do I handle third parties that operate security tooling for us?

Treat it as a third-party dependency: require contractual and technical proof of hardware separation for the security function they operate within your system boundary. Retain their attestations, architecture descriptions, and any configuration evidence you can obtain under the contract.

What’s the cleanest way to keep SC-3(1) evidence current?

Tie SC-3(1) to change management and recurring evidence tasks so every material change to the separated components produces an artifact. Many teams implement this in their GRC workflow; Daydream can track ownership, procedures, and evidence collection in one place. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5