SC-43: Usage Restrictions

To meet the sc-43: usage restrictions requirement, you must define which system components have special “do’s and don’ts,” publish implementation guidelines for how they may be used, and then enforce those rules with technical and procedural controls plus audit-ready evidence. Scope the components, write actionable restrictions, assign owners, and retain proof of operation. ¹

Key takeaways:

• SC-43 expects documented usage restrictions and implementation guidelines for specified system components, not informal tribal knowledge. ¹
• Auditors will look for enforcement: configuration, access paths, monitoring, exceptions, and recurring evidence tied to each restricted component.
• The fastest path is a component-by-component matrix mapping restrictions → enforcing control → owner → evidence cadence.

SC-43 sits in the System and Communications Protection (SC) family and is easy to under-implement because the text is short while the operational expectation is broad: you must explicitly govern how certain system components can be used. In practice, “system components” becomes your list of items that can create outsized security, privacy, resilience, or compliance risk if misused: administrative interfaces, remote access tooling, APIs, cryptographic modules, boundary devices, production databases, logging pipelines, and any specialized hardware or services that process federal data.

For a Compliance Officer, CCO, or GRC lead, the objective is straightforward: produce clear usage restrictions and implementation guidelines that engineering can follow, then prove those restrictions are enforced. The exam risk is equally straightforward: teams often have partial policies (“admins must be careful”) without a component-scoped ruleset and without evidence that the rules are implemented and monitored.

This page translates SC-43 into an operator-ready checklist: scope and inventory, define restrictions, build enforcing mechanisms, run an exception process, and collect evidence. It also shows how to package the work so an assessor can trace requirement → implementation → artifacts without guesswork. ²

Regulatory text

Excerpt (SC-43): “Establish usage restrictions and implementation guidelines for the following system components: {{ insert: param, sc-43_odp }} ; and” ¹

What this means for operators

• You must identify the “following system components” for your environment (the parameter is organization-defined in your system security plan and control definition) and then:
  1. Establish usage restrictions (what is allowed, prohibited, and conditional), and
  2. Establish implementation guidelines (how teams must configure and operate those components so the restrictions are consistently met). ¹

Treat SC-43 as a component-specific rulebook plus proof that the rulebook is followed.

Plain-English interpretation (what SC-43 is really asking)

SC-43 requires you to prevent risky or noncompliant use of sensitive or security-relevant components by setting explicit rules and making those rules real through configuration, access controls, and oversight.

A practical interpretation:

• If a component can materially change security posture or expose controlled data, you must define who can use it, for what purpose, from where, using what method, under what logging, and with what approvals.
• You must also define how engineers implement those requirements (standard configs, hardening steps, required integrations, and operational runbooks).
• You must be able to demonstrate it with evidence, not intentions. ¹

Who it applies to (entity and operational context)

Applies to:

• Federal information systems and contractor systems handling federal data that implement NIST SP 800-53 controls. ²

Operationally, it applies wherever you have:

• Production environments, regulated enclaves, or segmented networks handling federal data.
• Shared services and platforms that support those environments (IdP, SIEM, CI/CD, endpoint management, secrets management).
• Third-party-managed components if they are part of your system boundary or materially support the system (for example, a managed firewall, SaaS logging, or remote support tooling). You still need restrictions and guidelines, even if the third party performs the operations.

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

1) Define the SC-43 component scope (the “ODP” list)

Create a definitive list of system components covered by SC-43 for your system boundary. Start with:

• Administrative interfaces (cloud consoles, hypervisor consoles, Kubernetes control plane)
• Remote access components (VPN, ZTNA, bastions, RDP gateways)
• Boundary devices (firewalls, WAF, API gateways)
• Data movement paths (SFTP servers, message brokers, ETL tools)
• Key security services (PKI/HSM, secrets vault, IAM/IdP, EDR, SIEM)

Output artifact: “SC-43 Component Scope” list, owned by the system owner with security and platform engineering sign-off.

2) Write usage restrictions that are testable

For each in-scope component, write restrictions using a consistent template:

Restriction template (copy/paste)

• Permitted users/roles: (named roles, not “admins”)
• Permitted actions: (e.g., read-only, break-glass changes, key rotation)
• Prohibited actions: (e.g., direct production DB queries; disabling logs)
• Approved access paths: (e.g., via bastion only; via managed device only)
• Required approvals: (e.g., change ticket; incident commander)
• Required logging/retention hooks: (e.g., all admin actions to SIEM)
• Conditions: (time-bound access, MFA, source IP constraints)
• Exception process: who can grant, how documented, expiry requirement

Operator tip: avoid moral language (“should”). Write rules an auditor can map to a config setting, a ticket, or a log event.

Output artifact: “SC-43 Usage Restrictions Matrix” (component → restrictions).

3) Add implementation guidelines that engineers can follow without interpretation

For each restricted component, document:

• Baseline configuration standard (hardening settings, required integrations)
• How to provision access (JIT/PAM workflow, group membership, approvals)
• How to deploy changes (CI/CD guardrails, infrastructure-as-code patterns)
• Monitoring expectations (alerts for forbidden actions, drift detection)
• Operational runbooks (break-glass steps, emergency changes, rollback)

Output artifact: “SC-43 Implementation Guidelines” (can be a standards doc plus runbook links).

4) Map restrictions to enforcing controls (technical + procedural)

Create a traceable mapping:

Component	Restriction	Enforcement mechanism	Owner	Evidence
Cloud console	Only via SSO + MFA; no local users	IdP policies; disable local IAM users; conditional access	IAM lead	IdP policy export; IAM user list
Prod DB	No direct access from laptops	Network segmentation; bastion; DB firewall rules	Platform lead	Firewall rules; connection logs
CI/CD	Only signed artifacts to prod	Pipeline checks; branch protections; signing	DevOps lead	Pipeline config; release logs

This is where SC-43 passes audits: the restriction is tied to something you can demonstrate.

5) Stand up an exception and periodic review process

Auditors expect that restrictions are not static paperwork.

• Exception intake: ticket-based, with business justification and compensating controls.
• Approval authority: named role(s), not a team alias.
• Expiry: every exception has an end date and review trigger (your policy choice).
• Periodic review: confirm the component list is still accurate and restrictions still match architecture.

Output artifacts: exception tickets, approvals, and a review log.

6) Operationalize evidence collection (assessment-ready)

Define “what evidence proves SC-43 is operating” per component:

• Config exports or policy screenshots (with timestamps and system identifiers)
• Access control lists / group membership reports
• Change management records tied to restricted components
• Admin activity logs (who did what, when, from where)
• Monitoring alerts and incident tickets for violations or near-misses
• Exception register with approvals and expirations

If you use Daydream, the clean pattern is to map SC-43 to a control owner, attach the procedure, and schedule recurring evidence pulls per component so you do not rebuild an evidence package during the audit window. ¹

Required evidence and artifacts to retain (audit package checklist)

Minimum set most assessors expect to see, organized for fast retrieval:

1. SC-43 component scope list (what components are covered, and why)
2. Usage restrictions matrix (component-by-component restrictions)
3. Implementation guidelines (standards + runbooks)
4. Enforcement proof for each component (configs, policies, segmentation rules)
5. Access governance evidence (role definitions, approvals, PAM/JIT records)
6. Logging/monitoring evidence (admin logs, alert rules, sample events)
7. Exception register (requests, approvals, compensating controls, expiry)
8. Periodic review record (who reviewed, what changed, dates)

Common exam/audit questions and hangups

Expect questions like:

• “Which components are in scope for SC-43 in this system boundary, and who approved the list?” ¹
• “Show me one restricted component and walk me from restriction → guideline → technical enforcement → logs.”
• “How do you prevent administrators from bypassing the approved access path?”
• “How do you detect and respond to restricted actions (for example, policy changes, logging disabled, direct database access)?”
• “How are exceptions approved and time-bounded?”

Hangups that cause findings:

• Restrictions exist only in a general security policy, not per component.
• Guidelines exist, but they are not tied to enforcement mechanisms.
• Evidence is ad hoc and can’t be reproduced consistently.

Frequent implementation mistakes (and how to avoid them)

1. Mistake: scoping SC-43 to “network devices only.”
   Fix: include identity, admin interfaces, and data movement components. SC-43 is about usage, not just perimeter gear. ²

2. Mistake: writing restrictions that can’t be tested.
   Fix: every restriction should map to a configuration, an approval record, or a log query.

3. Mistake: exceptions handled in chat or email.
   Fix: require a ticket with approver, compensating controls, and expiry.

4. Mistake: no ownership model.
   Fix: assign a control owner plus component owners. SC-43 needs operational accountability.

5. Mistake: failing to align third-party operations.
   Fix: where a third party operates an in-scope component, contractually require adherence to your restrictions and provide you the evidence you need (config attestations, access logs, SOC reports where applicable).

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for SC-43, so this page does not cite enforcement outcomes. The practical risk is still clear: weak usage restrictions are a common root cause behind unauthorized administrative actions, uncontrolled data access paths, and unreviewed configuration changes. SC-43 reduces that exposure by forcing explicit rules and proof of enforcement. ²

Practical execution plan (30/60/90-day)

Your timeline depends on system complexity and authority-to-operate commitments. Use this as a sequencing plan, not a duration guarantee.

First 30 days (stabilize scope and documentation)

• Confirm the system boundary and compile the SC-43 component scope list.
• Draft the usage restrictions matrix for the highest-risk components first (admin access, remote access, production data stores).
• Assign owners for each component and for the SC-43 control.
• Choose the evidence set you will retain per component and where it will live.

Days 31–60 (enforce and instrument)

• Implement or tighten enforcement mechanisms (SSO/MFA policies, network segmentation, PAM/JIT, CI/CD protections).
• Build monitoring for restricted actions and produce sample log evidence.
• Launch the exception workflow and an exception register.

Days 61–90 (prove operation and make it repeatable)

• Run a tabletop audit: pick two components and walk restriction → guideline → enforcement → evidence.
• Close gaps where enforcement does not match the written restriction.
• Schedule recurring evidence collection and periodic review so SC-43 stays current through architecture changes.

Frequently Asked Questions

What counts as a “system component” for SC-43?

Treat any hardware, software, service, or interface in your system boundary that can materially affect security or data exposure as a component. Document your scoped list so an assessor can see what you included and why. ¹

Do we need a separate policy document for SC-43?

Not necessarily. Auditors need clear usage restrictions and implementation guidelines per component; that can live in standards, runbooks, and a single matrix if it is approved, versioned, and enforced. ¹

How do we show “implementation guidelines” without writing a long narrative?

Use short, actionable configuration standards plus links to runbooks and infrastructure-as-code repositories. The key is traceability from restriction to the steps engineers follow in real operations.

How do SC-43 restrictions relate to third parties that manage parts of our stack?

If a third party operates an in-scope component, your restrictions still apply. Put the restrictions into contractual requirements or operating procedures and require evidence you can retain (access logs, admin activity reports, configuration attestations).

What evidence is strongest for SC-43 in an assessment?

Component-scoped restrictions mapped to technical enforcement plus time-stamped artifacts: policy exports, configuration snapshots, access approvals, and logs showing controls in operation. ¹

How can Daydream help without turning this into a paperwork exercise?

Daydream can track SC-43 ownership, store the restriction-to-evidence mapping per component, and automate recurring evidence requests so you have an always-ready audit package instead of a scramble. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5