SC-25: Thin Nodes

To meet the sc-25: thin nodes requirement, you must identify the system components that qualify as “thin nodes” in your environment, then configure them to run only essential functions and store minimal information locally. Operationalize SC-25 by standardizing hardened builds, blocking local storage, and proving the configurations stay in place through continuous configuration monitoring. ¹

Key takeaways:

• Define which endpoints and edge components are in scope, then document the “minimal functionality” baseline for each thin-node class.
• Enforce technical controls that prevent local data storage and limit installed services, admin rights, and software execution.
• Keep assessor-ready evidence: build standards, configuration baselines, enforcement logs, exceptions, and periodic validation results.

SC-25 (Thin Nodes) is a design and configuration control that pushes you toward endpoints and edge devices that do less, store less, and expose less. The exam friction usually comes from ambiguity: teams assume “thin client” equals “compliant,” or they treat this as a procurement decision instead of an ongoing configuration requirement. Assessors will look for two things: (1) you explicitly identified the components where thin-node principles apply, and (2) you can prove those components are actually constrained in function and storage over time, not just at initial deployment. ²

This page is written for a Compliance Officer, CCO, or GRC lead who needs to translate SC-25 into a concrete checklist your endpoint, infrastructure, and security engineering teams can execute. The goal is simple: reduce the attack surface and data exposure created by endpoints and distributed components by stripping them to essentials, while keeping enough documentation and technical telemetry to answer audit questions quickly. ¹

Regulatory text

Control requirement (SC-25): “Employ minimal functionality and information storage on the following system components: {{ insert: param, sc-25_odp }}.” ¹

What the operator must do

1. Fill in the organization-defined parameter (ODP). The requirement explicitly expects you to name which system components must behave as thin nodes in your environment (for example: kiosks, VDI thin clients, call-center desktops, jump hosts, OT HMIs, field laptops used for regulated data, or point-of-sale devices). Your first compliance deliverable is the scope statement. ¹
2. Define “minimal functionality” for each in-scope class. “Minimal” is not a vibe; it’s a baseline configuration: allowed services, allowed apps, allowed ports, allowed peripherals, allowed admin actions. ¹
3. Ensure “minimal information storage” in practice. You must reduce or prevent local persistence of sensitive data on those components through configuration and architecture choices (e.g., redirect profiles to central storage, disable local caches where feasible, encrypt any required local data, and enforce secure wipe and session reset patterns where appropriate). ¹

Plain-English interpretation of the sc-25: thin nodes requirement

SC-25 expects you to treat certain components as “disposable interfaces,” not full-featured workstations. They should:

• Run only what’s needed for the mission (no extra apps, services, browsers/plugins, developer tooling, or background agents beyond what you approve).
• Store as little as possible locally (no local copies of regulated datasets, minimized logs and caches, controlled downloads, and controlled removable media).

If you can’t prevent local storage entirely, your compliance posture depends on showing you made a conscious, risk-based decision with compensating controls and documented exceptions.

Who it applies to (entity and operational context)

SC-25 is commonly assessed for:

• Federal information systems and systems aligned to NIST SP 800-53. ²
• Contractor systems handling federal data where NIST 800-53 controls are flowed down contractually or required by an authorization boundary. ²

Operationally, this control is most relevant anywhere you have:

• High endpoint count (enterprise desktops, call centers, distributed retail).
• Sensitive workflows performed on endpoints that are hard to physically secure.
• Shared-user devices (kiosks, nursing stations, shop-floor terminals).
• Remote access paths (VDI, privileged access workstations, jump boxes).

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

Use this as an execution runbook you can hand to endpoint/infrastructure owners.

Step 1: Establish scope and the thin-node classes

Create a short “SC-25 scope memo” with:

• In-scope component types (the ODP list).
• Ownership per class (endpoint engineering, EUC, IT ops, OT, etc.).
• Where each class lives (networks, sites, business units).
• A link to the authoritative asset inventory view that enumerates them.

Practical tip: If you cannot enumerate the population, you cannot credibly prove enforcement. Tie the scope to your CMDB/asset inventory and your device management platform.

Step 2: Define “minimal functionality” baselines per class

For each thin-node class, define:

• Approved applications (allow-list).
• Approved services/agents (EDR, management agent, VPN client, VDI client).
• Privilege model (no local admin for standard users; controlled break-glass).
• Security settings (host firewall on, logging on, screen lock, USB control).
• Network behavior (approved destinations, proxies, DNS, east-west limits).

Deliverable: a baseline standard (build standard or configuration standard) that is testable.

Step 3: Define “minimal information storage” rules per class

Write explicit rules such as:

• Where user profiles live (roaming profile, folder redirection, VDI).
• Whether local downloads are blocked or redirected.
• Whether clipboard, drive mapping, and local printing are restricted for remote sessions.
• How caching is handled (browser cache limits, DLP controls, app cache policies).
• What local logging is allowed and for how long (keep this qualitative unless your org already has a standard; don’t invent retention numbers).

If any data must reside locally (offline mode, field operations), specify:

• Encryption requirements and key management approach.
• Remote wipe capability.
• Session timeout and auto-lock.
• Secure decommission and media sanitization linkage.

Step 4: Implement technical enforcement

Common enforcement patterns that map cleanly to SC-25:

• Gold images / hardened builds for thin-node classes.
• Application control (allow-listing) aligned to the baseline.
• Device management configuration profiles (MDM/UEM policies).
• Least privilege enforcement and privileged access workflows.
• Data controls (DLP, browser download restrictions, controlled removable media).
• Centralized compute patterns (VDI/RDS, published apps) to reduce local processing and storage.

Step 5: Exception handling (make it auditable)

Create an SC-25 exception record template:

• Component ID(s) and owner.
• Business justification.
• What additional function/storage is needed and why.
• Compensating controls (encryption, monitoring, additional network controls).
• Approval and review cadence (state it as “periodic” if you don’t have a formal cadence, then formalize later).

Assessors accept exceptions when they are controlled; they reject exceptions that look like unmanaged drift.

Step 6: Validate continuously and report

Build a lightweight control monitoring loop:

• Compare live configurations against the baseline (configuration compliance reports).
• Detect prohibited software/services.
• Detect local data locations that violate policy (where technically feasible).
• Track population coverage (how many in-scope assets are under management and compliant).

Daydream fit (earned mention): Many teams fail SC-25 on evidence, not intent. Daydream can help you map SC-25 to a named control owner, document the implementation procedure, and generate a recurring evidence checklist so your device compliance reports and exception approvals are collected consistently.

Required evidence and artifacts to retain

Keep artifacts that answer: “What is in scope, what is the baseline, how is it enforced, and how do you know it stayed enforced?”

Minimum evidence set:

• SC-25 scope memo with the ODP component list (the filled-in “following system components”). ¹
• Thin-node baseline standards per class (build standard/configuration baseline).
• Configuration enforcement proof: MDM/UEM policy exports, GPOs (if applicable), configuration profiles, application control policies.
• Device compliance reports showing drift and remediation actions.
• Software inventory snapshots for in-scope classes (to prove “minimal functionality”).
• Data storage controls evidence: DLP policies, download restrictions, encryption policies, remote wipe capability proof.
• Exception register and approvals with compensating controls and review notes.
• Change management records for baseline updates (who approved, what changed, why).

Common exam/audit questions and hangups

Expect these questions, and prepare one-slide answers with links to evidence:

1. “Which components are your thin nodes?”
   Hangup: teams describe a concept but cannot list the actual population. Bring the ODP scope list plus an asset inventory export.

2. “Define minimal functionality.”
   Hangup: “We hardened them” without a written baseline. Provide allow-listed apps/services and privilege settings per class.

3. “Show me minimal information storage.”
   Hangup: teams rely on user training. Provide technical restrictions, redirections, and evidence of local storage controls.

4. “How do you detect drift?”
   Hangup: one-time hardening with no monitoring. Provide configuration compliance reports and remediation tickets.

5. “How do exceptions work?”
   Hangup: informal approvals in chat. Provide an exception register and an approval workflow.

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails SC-25	How to avoid it
Calling a device “thin” because it’s low-cost hardware	SC-25 is about functionality and storage limits, not purchase price	Define baselines and prove enforcement with configuration evidence
No explicit ODP scope	The control text expects you to name components	Publish a scope memo and tie it to asset inventory
Allowing local admin “for convenience”	Admin rights expand functionality and persistence	Use least privilege; define break-glass procedures
Blocking storage in policy but not in tech	Audits test reality, not intent	Enforce with DLP/MDM and validate with scans/reports
Exceptions without compensating controls	Exceptions become permanent bypasses	Require encryption/monitoring/wipe, and track approvals

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for SC-25, so you should treat this as an assessment-readiness and risk-reduction control rather than a “headline enforcement” item.

Risk implications that matter operationally:

• Reduced data exposure from endpoint loss/theft when little to no sensitive data is stored locally.
• Reduced attack surface when unnecessary services and apps are removed.
• Improved containment when thin nodes are easier to rebuild and reset to a known-good state.

A practical 30/60/90-day execution plan

Use these phases as an operator’s roadmap. Convert them into your internal project plan with owners and dates.

First 30 days (Immediate)

• Appoint a control owner and technical owners per thin-node class. ¹
• Publish the SC-25 scope memo (ODP list) and pull an inventory of in-scope assets.
• Draft minimal functionality and minimal storage baselines for one high-impact class (often kiosks, shared workstations, or privileged access workstations).
• Stand up an exception register and approval path.

Next 60 days (Near-term)

• Implement baseline enforcement through your endpoint management stack for the first class.
• Produce the first configuration compliance report and remediate drift.
• Expand baselines to remaining in-scope classes.
• Validate data storage controls with spot checks (device sampling) and tooling outputs where available.

Next 90 days (Operationalize)

• Convert baselines into “policy-as-config” where feasible: versioned configurations, change control, and repeatable deployment.
• Establish recurring evidence collection (compliance reports, software inventory, exception reviews).
• Add SC-25 to onboarding for new device classes and procurement standards so thin-node constraints are default, not retrofit.

Frequently Asked Questions

Does SC-25 require that we use VDI or thin clients?

No. SC-25 requires minimal functionality and minimal local information storage on specified components, regardless of whether they are VDI endpoints or full laptops. VDI is one common way to meet the storage objective. ¹

What counts as a “thin node” in practice?

Your organization defines the in-scope components via the SC-25 parameter list. Common candidates are shared-use endpoints, kiosks, jump hosts, and endpoints used to access sensitive systems where local storage is a risk. ¹

How do we prove “minimal information storage” to an auditor?

Show technical restrictions (configuration profiles, DLP/download controls, encryption where local data is unavoidable) plus validation outputs (compliance reports, scans, or checks). Pair this with an exception register for any approved local storage. ¹

We have field devices that must work offline. Are we automatically noncompliant?

No. Document the business requirement, limit what is stored locally, encrypt it, and add compensating controls such as remote wipe and enhanced monitoring. Track the decision as a formal exception with periodic review. ¹

Who should own SC-25: security or IT?

Assign a single control owner in GRC/security for accountability, then name technical owners for endpoint engineering and any specialized environments (OT, retail, call centers). Auditors want clear ownership and repeatable evidence. ²

What’s the fastest way to get assessment-ready for SC-25?

Start by scoping the in-scope components and writing one enforceable baseline for the highest-risk class, then produce a compliance report that proves enforcement. Use a tool like Daydream to standardize the control narrative, ownership, and recurring evidence requests across teams. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5