SC-4: Information in Shared System Resources

To meet the sc-4: information in shared system resources requirement, you must prevent sensitive data from one user, workload, or tenant being exposed to another through shared resources like memory, storage, caches, or temporary files. Operationalize SC-4 by inventorying shared resources, setting technical safeguards (isolation, sanitization, secure deletion), and retaining evidence that these safeguards are configured, tested, and monitored.

Key takeaways:

• SC-4 is about data remanence and cross-tenant/user leakage through shared compute and storage resources.
• Your fastest path is a shared-resource map + hardening standards + verification testing tied to systems in scope.
• Auditors look for repeatable proof: configuration baselines, test results, and ongoing checks mapped to an owner.

SC-4 is a “silent failure” control: nothing looks broken until data from one process, user, or tenant shows up where it should not. The requirement targets a specific risk pattern: shared system resources (memory, disk blocks, CPU caches, containers, virtual hosts, SaaS multi-tenant services) can unintentionally retain or expose information if isolation and sanitization are weak.

For a Compliance Officer, CCO, or GRC lead, the goal is not to become a kernel engineer. The goal is to make sure engineering teams can prove three things: (1) you know where shared resources exist in your environment, (2) you have standards and technical controls to prevent residual data exposure, and (3) you verify the controls keep working through testing and operational monitoring.

SC-4 shows up in federal environments and contractor systems handling federal data, but the operational patterns apply broadly anywhere you run multi-user systems, virtualization, containers, or managed cloud services. Your best outcome is an auditable implementation that ties ownership, procedures, and recurring evidence into the systems you actually run.

Regulatory text

Requirement: “Prevent unauthorized and unintended information transfer via shared system resources.” ¹

What the operator must do

You must implement technical and procedural controls that stop data from “bleeding” between security boundaries through shared resources. Practically, that means:

• Isolation: Enforce separation between tenants/users/workloads on shared infrastructure.
• Sanitization: Clear or securely overwrite shared resources before reuse (memory, temporary storage, virtual disks, object reuse, print spools, job queues).
• Verification: Test and monitor to detect misconfiguration, drift, or provider failures that could reintroduce the risk.
  (Framework reference: Source: NIST SP 800-53 Rev. 5)

Plain-English interpretation

SC-4 requires you to prevent one party from seeing another party’s data because the system reused a shared resource without properly clearing it or separating access. Think of:

• A new container reading leftover data from a prior container via an improperly isolated volume mount.
• A deprovisioned VM disk being reattached without secure wipe.
• Temporary files, caches, or spool directories readable across users due to permissions or misconfigured services.
• Multi-tenant SaaS or PaaS services where configuration errors allow cross-tenant access.

This control is closely tied to how you build and operate systems. Policies alone will not satisfy it. You need defensible technical implementation plus operational evidence.

Who it applies to (entity and operational context)

SC-4 is commonly assessed in:

• Federal information systems and systems inheriting federal requirements. ²
• Contractor systems handling federal data, including cloud-hosted workloads supporting federal missions or processing federal information. ²

Operationally, SC-4 applies wherever you have shared compute or storage:

• Virtualized environments (hypervisors, shared hosts)
• Containers and orchestration (Kubernetes, shared worker nodes)
• Shared databases or caching tiers
• Shared file services (NFS/SMB), object storage, shared CI/CD runners
• Managed cloud services where the provider controls some layers and you configure access, tenancy, and data handling

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

1) Assign ownership and define scope

• Assign a control owner (usually Security Engineering or Infrastructure) and a GRC owner accountable for evidence quality.
• Define “systems in scope” using your boundary definition (ATO boundary, enclave, product environment, or other authorized boundary).
• Decide your shared-resource categories to assess consistently: memory, local disk, network storage, caches, temporary directories, snapshots/backups, queues/spools, and cloud provider constructs.

Deliverable: SC-4 control record with owner, in-scope systems, and evidence cadence mapped to your program. ¹

2) Build a shared resource map ¹

Create a short, auditable inventory that answers: “Where do multiple security principals share a resource?” Include:

• Compute: hypervisor clusters, node pools, shared runners
• Storage: shared volumes, ephemeral disks, object buckets, backup repositories
• Data services: shared DB instances, caches, message brokers
• Workspace services: shared VDI hosts, bastion/jump boxes
• SaaS: tenancy model and admin boundary assumptions

Tip: Keep it readable. Auditors want clarity more than exhaustiveness.

Deliverable: Shared Resource Register (system → resource type → isolation mechanism → sanitization method → responsible team).

3) Set engineering standards for isolation

Implement and document baseline requirements such as:

• Strong tenant and workload separation (accounts/projects/namespaces with least privilege)
• Default-deny permissions on shared files and temp paths
• Segregated secrets, service accounts, and IAM roles per environment
• Prohibited patterns (for example: shared admin accounts, world-readable scratch directories, reusing storage without wipe)

Deliverable: Configuration standards (hardening guide) that explicitly addresses shared resources and cross-boundary data exposure.

4) Implement sanitization and secure disposal controls

Focus on what actually causes leakage:

• Ephemeral storage and temp files: enforce secure handling, permissions, and cleanup on job completion.
• Persistent storage reuse: require secure wipe or cryptographic erase before reassignment.
• Snapshots and backups: restrict access, validate isolation, and ensure deletion workflows actually remove access.
• Memory and caching layers: rely on platform-level isolation controls and validate they are enabled and not overridden.

In cloud contexts, your control often becomes “verify provider capability + enforce correct configuration.” Capture the shared responsibility line clearly.

Deliverable: Runbooks and automated workflows for deprovisioning and sanitization (tickets, scripts, or infrastructure-as-code controls).

5) Validate with test cases that mirror real failure modes

Testing should prove you prevent unintended transfer, not just that a setting exists. Examples of practical tests:

• Attempt cross-namespace volume mounts and verify policy blocks the action.
• Validate temp directories are not readable across users on shared hosts.
• Deprovision and reprovision storage in a lower environment and verify prior data is not recoverable through standard means.
• Review container runtime settings to confirm hostPath restrictions and node isolation controls.

Deliverable: SC-4 verification test results and remediation logs for failures found.

6) Operationalize: monitor, review, and keep evidence current

SC-4 degrades through drift. Put it on rails:

• Config drift detection for IAM, storage permissions, and platform guardrails
• Change management hooks so new shared services trigger a SC-4 review
• Periodic evidence collection (screenshots, exports, policy-as-code reports, test runs)

Daydream fit (earned): Many teams fail SC-4 on “missing implementation evidence.” Daydream helps by mapping SC-4 to an owner, a documented procedure, and recurring evidence artifacts so your assessor sees a repeatable control instead of a one-time project. ¹

Required evidence and artifacts to retain

Retain artifacts that show design, implementation, and operation:

1. Control ownership and procedure

• Control narrative: how you prevent unintended transfer via shared resources
• RACI/ownership and escalation path
• Change triggers (what events require review)

2. Shared Resource Register

• System boundary and shared resource inventory
• Isolation and sanitization methods per resource

3. Technical proof

• Infrastructure-as-code policies, guardrails, and configuration baselines
• Access control exports (IAM role bindings, bucket policies, file permission baselines)
• System hardening standards that address shared temp paths, storage reuse, and tenant boundaries

4. Validation evidence

• Test plans and results
• Findings and remediation tickets
• Exception register for unavoidable shared resources, with compensating controls

5. Ongoing operations

• Drift monitoring outputs
• Periodic review records
• Change management tickets showing SC-4 impact assessment

Common exam/audit questions and hangups

Auditors and assessors often focus on these points:

• “Show me where shared resources exist.” If you cannot enumerate them, you look like you guessed.
• “How do you prevent data remanence?” Expect follow-ups on deprovisioning, volume reuse, snapshots, and ephemeral storage.
• “How do you know it stays effective?” Configuration screenshots without monitoring and tests often fail.
• Boundary confusion: If you rely on a cloud provider control, you must show what you configure and what you inherit, aligned to your authorization boundary. ²

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails	How to fix it
Treating SC-4 as a policy-only control	SC-4 is technical and must be provable	Tie to platform guardrails, hardening standards, and test evidence
No shared resource inventory	You cannot demonstrate coverage	Create a Shared Resource Register and maintain it through change management
Ignoring “temporary” paths and job artifacts	Real leaks often occur in scratch space	Standardize temp directory permissions and cleanup in build/run pipelines
Assuming cloud provider isolation covers everything	Misconfiguration is your problem	Document the responsibility split and keep configuration exports as evidence
One-time testing only	Drift reintroduces exposure	Add recurring checks and keep evidence current

Risk implications (why SC-4 gets attention)

SC-4 failures can create:

• Confidentiality breaches across tenants, customers, or internal teams
• Regulatory scope expansion after an incident (more systems pulled into review)
• Authorization and customer trust issues in federal and regulated contexts

The risk is especially acute in multi-tenant architectures, shared analytics platforms, shared CI/CD runners, and environments with frequent provisioning and deprovisioning.

Practical 30/60/90-day execution plan

First 30 days (stabilize and define)

• Assign SC-4 control owner and GRC owner; document the control narrative. ¹
• Identify in-scope systems and build the initial Shared Resource Register.
• Decide baseline requirements for isolation and sanitization (draft standards).
• Pick initial verification tests based on your highest-risk shared services.

Days 31–60 (implement and verify)

• Implement guardrails and baselines: IAM boundaries, storage permissions, platform policies, deprovisioning workflows.
• Run verification tests; log findings and remediation actions.
• Set up evidence collection: configuration exports, policy-as-code reports, and runbook references.
• Stand up an exception process for legacy constraints, with compensating controls.

Days 61–90 (operationalize and prepare for assessment)

• Add drift detection and recurring reviews for high-risk shared resources.
• Integrate SC-4 checks into change management (new shared service requires review and entry in the register).
• Package an assessor-ready evidence set: register, standards, test results, and operational monitoring outputs.
• Use Daydream (or your GRC system) to track owners, tasks, and recurring artifacts so evidence stays current between audits. ¹

Frequently Asked Questions

Does SC-4 apply if we are “single tenant” but run multiple internal teams on shared infrastructure?

Yes. SC-4 targets unintended transfer between security principals, which can include internal users, teams, and environments sharing hosts, storage, or services. Treat internal segmentation failures the same way you would treat cross-customer exposure.

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

Anything reused across users or workloads without a clean separation boundary: memory, disk blocks, volumes, caches, temp directories, snapshots, queues, and shared cloud service instances. Your Shared Resource Register should list the concrete services and components you run.

Can we inherit SC-4 from our cloud provider?

You can inherit parts, but not all. You still must show how your configuration prevents unintended transfer (for example, IAM boundaries, storage policies, namespace isolation) and what provider assurances you rely on. ²

What evidence is most persuasive to an assessor?

A maintained shared-resource inventory, explicit engineering standards, and test results that demonstrate prevention of cross-boundary data access. Pair this with recurring operational evidence (drift monitoring, periodic reviews) tied to an accountable owner.

How do containers and Kubernetes change SC-4 implementation?

Containers increase the risk of misconfigured mounts, node sharing, and weak namespace controls. Focus on node pool separation for sensitive workloads, strict policies on volume mounts, and verification tests that attempt cross-namespace access and fail as designed.

We have legacy shared file servers. Can we meet SC-4 without replacing them?

Usually yes, but you need compensating controls: strict access control lists, segregation of sensitive data, hardened temp/spool directories, strong logging, and periodic permission reviews. Document exceptions and show a plan to reduce exposure over time.

Footnotes

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

2. NIST SP 800-53 Rev. 5