03.13.04: Information in Shared System Resources

To meet the 03.13.04: information in shared system resources requirement, you must prevent one user’s or process’s data from being exposed through shared resources like memory, storage, caches, temporary files, print spools, and multi-tenant services. Operationally, this means configuring systems to clear, isolate, or cryptographically protect shared-resource data, then keeping evidence that those settings are in place and working. (NIST SP 800-171 Rev. 3)

Key takeaways:

• Treat “shared resources” broadly: RAM, disk, virtualized hosts, containers, shared SaaS tenants, temp directories, and job queues. (NIST SP 800-171 Rev. 3)
• Your control must be technical and provable: secure erase, zeroization, access isolation, and hardened configurations with logs/screenshots. (NIST SP 800-171 Rev. 3)
• Assessors will ask “where can data linger?” and “show me it’s cleared or isolated” across endpoints, servers, and cloud workloads. (NIST SP 800-171 Rev. 3)

03.13.04 focuses on a failure mode that looks mundane in architecture diagrams but becomes painful in incident response: data remnants. In real environments, Controlled Unclassified Information (CUI) can persist in places teams do not routinely inventory, such as OS swap, hypervisor snapshots, application caches, temporary directories, crashed-process core dumps, shared build agents, and managed service backends. That’s what “shared system resources” points at: resources reused across users, sessions, or tenants, where leftover data can be read by someone who should not have it. (NIST SP 800-171 Rev. 3)

For a Compliance Officer, CCO, or GRC lead, this requirement is about turning a broad security expectation into checkable implementation tasks: identify shared resources in your CUI scope, set configuration standards that prevent residual exposure, verify those standards via technical evidence, and keep that evidence ready for an assessment. (NIST SP 800-171 Rev. 3)

This page gives you requirement-level implementation guidance you can hand to IT, platform, and security engineering without translating it into abstract policy language. It also flags where audits commonly stall: unclear scoping, overreliance on “cloud provider handles it,” and missing proof that clearing/isolation actually occurs. (NIST SP 800-171 Rev. 3)

Regulatory text

Requirement: “NIST SP 800-171 Rev. 3 requirement 03.13.04 (Information in Shared System Resources).” (NIST SP 800-171 Rev. 3)

What the operator must do

You must protect information from unauthorized disclosure through shared system resources. In practice, that means:

• Identify where CUI could be written to or cached in resources reused by others (local or remote).
• Configure systems to isolate those resources per user/tenant/session and clear or zeroize them on release.
• Verify the settings and behaviors are present in the actual environment, not just in a standard.
• Retain evidence that shows the control is implemented and operating for in-scope systems and services. (NIST SP 800-171 Rev. 3)

Plain-English interpretation (what 03.13.04 is really asking)

Treat any reusable system component as a potential “data leftover” channel. If a resource is shared (or reused) and can store data, you need controls so one user/process/tenant cannot recover another’s CUI from that resource.

Shared system resources you should assume are in scope unless you can justify exclusion:

• Memory: RAM pages, GPU memory, shared memory segments, pagefile/swap, hibernation files.
• Storage and OS artifacts: temporary folders, application caches, browser caches, crash dumps, print spoolers, clipboard history, indexing services.
• Virtualization/container layers: VM images, snapshots, persistent volumes, node-level logs, container overlay filesystems.
• Multi-user/multi-tenant services: shared jump hosts, CI/CD runners, VDI farms, shared databases, shared file services.
• Job queues and pipelines: message queues, ETL staging, batch processing scratch space. (NIST SP 800-171 Rev. 3)

If you handle CUI, assume assessors will expect you to show you looked for these channels and made deliberate choices. (NIST SP 800-171 Rev. 3)

Who it applies to

Entities: Federal contractors and other nonfederal organizations that process, store, or transmit CUI in nonfederal systems. (NIST SP 800-171 Rev. 3)

Operational context: Any environment where CUI touches:

• End-user computing (workstations, laptops, mobile where permitted)
• On-prem servers (file servers, app servers, DB servers)
• IaaS/PaaS/SaaS workloads that store or process CUI
• Shared admin services (bastions, privileged workstations)
• Dev/test pipelines where production-like data or CUI is present (including logs and artifacts) (NIST SP 800-171 Rev. 3)

Common “you still own it” scenarios

• You host CUI in a SaaS app: you still must address configuration, tenancy controls, export paths, logging, and contractual assurances about isolation and media sanitization where relevant.
• You use shared infrastructure internally (VDI, build agents, terminal servers): you must manage cross-user isolation and cleanup between sessions. (NIST SP 800-171 Rev. 3)

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

Step 1: Define your “shared resource” inventory for the CUI boundary

Create a short register tied to your CUI system boundary that answers:

• What systems process/store/transmit CUI?
• What resources are reused across users, sessions, or tenants?
• Where does data land temporarily (temp, cache, swap, queue, spool, build artifacts)?
• Who administers each component (internal team vs third party)? (NIST SP 800-171 Rev. 3)

Output artifact: “Shared System Resources Register” (table format is fine).

Step 2: Set technical standards for isolation and clearing

Publish configuration requirements that engineers can implement consistently. Examples (adapt to your stack):

• Endpoints: disable or restrict local caching of sensitive docs; control clipboard/print spooling for CUI workflows; manage crash dumps; encrypt local disks.
• Servers: restrict and monitor /tmp-like directories; disable unnecessary services that cache content; ensure swap is encrypted where feasible.
• Virtualization/containers: enforce tenant isolation controls; prevent workload co-tenancy where you cannot assert isolation; set log retention and scrubbing rules.
• CI/CD: prevent CUI in build logs; scrub artifacts; isolate runners per project; destroy ephemeral runners after jobs; prevent shared workspace reuse without wipe. (NIST SP 800-171 Rev. 3)

Control design rule: prefer technical enforcement (configuration management, policies-as-code, platform guardrails) over “users must remember to delete temp files.”

Step 3: Implement on “highest risk first” components

Prioritize places where residual data exposure is realistic:

1. Shared interactive systems (VDI, jump boxes, terminal servers)
2. Multi-tenant or pooled compute (Kubernetes nodes, shared runners, shared VM hosts)
3. Systems that generate artifacts automatically (logging, printing, crash reporting)
4. Endpoints with local sync/caching (offline folders, browser caches) (NIST SP 800-171 Rev. 3)

Step 4: Verify the control with concrete tests

Verification needs at least one of each:

• Config verification: screenshots/exports of settings, policy objects, IaC repos, MDM profiles, hardening baselines.
• Behavior verification: demonstrate cleanup/isolation in a test workflow (for example, session teardown removes temp artifacts; spool directories are access-controlled; ephemeral runners are destroyed and not reused).
• Access verification: show that a different user cannot read remnants (permission checks, namespace isolation checks, role separation evidence). (NIST SP 800-171 Rev. 3)

Step 5: Operationalize as recurring evidence collection

Set a recurring control check that pulls:

• A sample of in-scope systems and verifies the baseline is applied
• Exception list review (systems that cannot meet the standard yet)
• Third-party attestations and contract language review for shared services handling CUI (NIST SP 800-171 Rev. 3)

Daydream fits here as the workflow layer: map 03.13.04 to your policy, assign implementation owners, and collect recurring evidence (config exports, screenshots, test records) on a schedule so assessment prep does not become a scramble. (NIST SP 800-171 Rev. 3)

Required evidence and artifacts to retain

Keep evidence tied to the CUI system boundary and to specific technologies.

Minimum evidence set (practical):

• Shared System Resources Register (systems, shared resources, owner, control approach)
• Secure configuration standard/baseline that addresses shared resource handling
• Implementation proof per platform (MDM profiles, GPOs, hardening scripts, IaC snippets, platform settings exports)
• Verification records (test steps, results, dates, tester, systems tested)
• Exceptions/risk acceptances with compensating controls and target remediation plan
• Third-party documentation and contract artifacts relevant to isolation/tenant separation and media handling, where applicable (NIST SP 800-171 Rev. 3)

Common exam/audit questions and hangups

Expect questions like:

• “Show me where CUI can be cached or written temporarily in this environment.” (NIST SP 800-171 Rev. 3)
• “How do you prevent one VDI user from accessing another’s temp files or clipboard/spool artifacts?”
• “Do build logs, debug dumps, or APM traces contain CUI? Show controls.”
• “For cloud services, what proves tenant isolation and sanitization practices? Where is it documented and approved?”
• “Show evidence this is checked periodically, not configured once and forgotten.” (NIST SP 800-171 Rev. 3)

Hangups that slow audits:

• No written inventory of shared resources; teams rely on tribal knowledge.
• Evidence exists but is not tied to the CUI boundary (assessor cannot tell what’s in scope).
• “The provider handles it” with no supplier due diligence artifacts. (NIST SP 800-171 Rev. 3)

Frequent implementation mistakes (and how to avoid them)

1. Treating this as only “disk sanitization.”
   Fix: include memory, caches, spools, logs, and ephemeral infrastructure in scope. (NIST SP 800-171 Rev. 3)

2. Ignoring CI/CD and observability pipelines.
   Fix: explicitly ban CUI in logs where possible; add automated scanning/redaction and artifact cleanup requirements.

3. Allowing shared admin workstations/jump hosts without session hygiene.
   Fix: enforce per-admin accounts, separate profiles, and session teardown cleanup; block copying CUI into shared locations.

4. No exception process.
   Fix: document what cannot be met, why, what compensates, and who accepted the risk. Keep it current. (NIST SP 800-171 Rev. 3)

5. Evidence is screenshots only, no proof of operation.
   Fix: add a lightweight verification test record showing the setting works (access denied, artifact removed, runner destroyed). (NIST SP 800-171 Rev. 3)

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement. (NIST SP 800-171 Rev. 3)

Risk-wise, 03.13.04 failures create “silent” data exposure: a user with legitimate access to a shared host, service account, or tenant-adjacent workload can recover remnants without triggering obvious perimeter alerts. The impact is higher when CUI appears in logs, caches, and artifacts that have broader reader access than the source system. (NIST SP 800-171 Rev. 3)

Practical 30/60/90-day execution plan

First 30 days: establish scope and baseline

• Build the Shared System Resources Register for the CUI boundary (start with top systems and shared services). (NIST SP 800-171 Rev. 3)
• Write a one-page engineering standard: what must be isolated, what must be cleared, where CUI is prohibited (logs, test data, shared scratch).
• Identify quick wins: restrict temp directories, lock down print spooling for CUI workflows, limit clipboard/drive redirection in VDI, and tighten logging content rules.

Next 60 days: implement and verify on priority systems

• Apply baseline controls to shared interactive systems and shared compute pools first. (NIST SP 800-171 Rev. 3)
• Add CI/CD controls: runner isolation, artifact retention rules, and automated cleanup.
• Run verification tests and capture evidence for a representative sample across endpoints, servers, and cloud workloads.

By 90 days: operationalize and make it repeatable

• Formalize exceptions and remediation backlogs with owners and milestones. (NIST SP 800-171 Rev. 3)
• Set recurring evidence collection: monthly/quarterly checks depending on change velocity, plus checks after major platform changes.
• In Daydream, map 03.13.04 to the specific systems, assign control owners, and attach evidence requests so the control stays audit-ready. (NIST SP 800-171 Rev. 3)

Frequently Asked Questions

Does 03.13.04 apply if we “only” store CUI in a SaaS platform?

Yes, because shared resources exist in SaaS and in your endpoints and admin workflows. You still need configuration controls, documented assurances from the provider where relevant, and evidence tied to your CUI boundary. (NIST SP 800-171 Rev. 3)

What counts as a “shared system resource” in practice?

Any reusable component where data can persist and be accessed later by a different user/process/tenant: temp folders, caches, swap, spools, shared compute nodes, shared runners, and shared service backends. Treat “shared” broadly and document your interpretation. (NIST SP 800-171 Rev. 3)

Is full-disk encryption enough to satisfy 03.13.04?

Encryption helps, but it does not automatically address cross-user exposure on the same running system, shared temp locations, or multi-tenant services. Pair encryption with isolation, least privilege, and cleanup behaviors you can demonstrate. (NIST SP 800-171 Rev. 3)

How do we handle shared CI/CD runners that might process CUI?

Prefer ephemeral, isolated runners per job or per project, with workspace cleanup and artifact controls. Add verification evidence that jobs cannot read prior workspaces and that logs/artifacts do not retain CUI unnecessarily. (NIST SP 800-171 Rev. 3)

What evidence do assessors accept for “clearing” shared resources?

Configuration exports and hardening settings are a start, but add a short verification record showing the intended behavior (for example, temp artifacts removed after session end or permissions prevent access by a different user). Keep results tied to in-scope system identifiers. (NIST SP 800-171 Rev. 3)

We have legacy systems where cleanup is hard. Can we document an exception?

You can document an exception with compensating controls and a remediation plan, but keep it specific: what data can persist, who could access it, and what you do to reduce likelihood and impact. Track it as an active risk item, not a one-time memo. (NIST SP 800-171 Rev. 3)