SC-34(1): No Writable Storage

SC-34(1): No Writable Storage requires you to deploy the selected SC-34 countermeasure (the organization-defined parameter) in a way that prevents any writable storage from persisting across restarts or power cycles. Operationally, that means designing the component so it cannot retain attacker-injected state, logs, configs, or data after reboot, and proving it with build settings, technical testing, and runbook controls. (NIST SP 800-53 Rev. 5 OSCAL JSON)

Key takeaways:

• Treat SC-34(1) as an engineering constraint: “no persistent write path” across reboot for the relevant component(s). (NIST SP 800-53 Rev. 5 OSCAL JSON)
• Scope precisely which components implement the SC-34 mechanism, then lock down storage, configuration, and logging patterns to be non-persistent or externally managed. (NIST SP 800-53 Rev. 5 OSCAL JSON)
• Evidence is the control: architecture diagrams, immutable configuration proofs, test results, and operational runbooks mapped to a named control owner. (NIST SP 800-53 Rev. 5)

SC-34 sits in the System and Communications Protection family and is typically assessed in environments where integrity and resilience matter: federal information systems and contractor systems that handle federal data. For SC-34(1): no writable storage requirement, the practical question a CCO or GRC lead must answer is simple: “Which security mechanism are we calling SC-34, and can it write anything that survives a restart?” If the answer is “yes,” you either redesign the component or you constrain it so writes are ephemeral.

This requirement shows up in real programs as an “immutability” expectation. Assessors will look for places where persistent state can be used against you: malware surviving a reboot, configuration drift, tampered rulesets, or attacker-planted scripts that re-run after power cycling. The control text is short, but implementing it touches architecture (where state lives), platform configuration (read-only filesystems, immutable images), operations (how updates happen), and monitoring (where logs go if not local).

This page is written to help you operationalize sc-34(1): no writable storage requirement quickly: scope it, assign ownership, implement technical guardrails, and collect assessment-ready evidence. (NIST SP 800-53 Rev. 5; NIST SP 800-53 Rev. 5 OSCAL JSON)

Regulatory text

Text (verbatim): “Employ {{ insert: param, sc-34.01_odp }} with no writeable storage that is persistent across component restart or power on/off.” (NIST SP 800-53 Rev. 5 OSCAL JSON)

What the operator must do

1. Identify the SC-34 mechanism referenced by the organization-defined parameter (ODP). This is the thing you are “employing” for SC-34 in your system design (for example, a specific anti-tamper mechanism, integrity validation component, or other SC-34 technical approach defined in your SSP/control narrative). (NIST SP 800-53 Rev. 5 OSCAL JSON)
2. Ensure that mechanism has no persistent writable storage across a restart or power cycle. Any writable storage that survives reboot violates the enhancement for the component in scope. (NIST SP 800-53 Rev. 5 OSCAL JSON)
3. Prove it through configuration, architecture, and tests that demonstrate the absence of persistent write paths. (NIST SP 800-53 Rev. 5)

Plain-English interpretation (what “no writable storage” really means)

For the component(s) implementing the SC-34 mechanism, you must design and configure them so they cannot retain writes locally after restart. If something can be modified (written) and that modification is still present after reboot, you need to either:

• make that storage read-only, or
• make it ephemeral (cleared on reboot), or
• move state to an external system that is not part of the component’s local persistent storage (and then confirm SC-34(1) scope remains satisfied for the component under assessment). (NIST SP 800-53 Rev. 5 OSCAL JSON)

What tends to surprise teams: “writable storage” is broader than data files. It includes local config overrides, cached rulesets, local databases, scheduled tasks, startup scripts, plugins, and any “helpful” local persistence that makes operations easier but creates a foothold.

Who it applies to (entity and operational context)

Entity types in scope: federal information systems and contractor systems handling federal data. (NIST SP 800-53 Rev. 5 OSCAL JSON)

Operational contexts where SC-34(1) commonly bites:

• Appliances, hardened virtual machines, or containers providing a protective function where local persistence can become an attack primitive.
• Mission or safety-relevant components where a reboot should restore a known-good state.
• Hosted platforms where teams rely on mutable instances rather than immutable images. (NIST SP 800-53 Rev. 5)

Roles typically involved

• Control owner (accountable): Security Architecture, Platform Security, or the service owner for the component implementing SC-34.
• Implementers: SRE/Platform Engineering, OS hardening engineers, CI/CD owners.
• Assurance: GRC team validating scope, evidence quality, and assessment mapping.

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

1) Define scope and the organization-defined parameter (ODP)

• Find the SC-34 narrative in your SSP, system security plan, or control implementation statement.
• Name the mechanism that corresponds to sc-34.01_odp (the ODP placeholder in the catalog text). Put the exact mechanism name in your control record and architecture docs. (NIST SP 800-53 Rev. 5 OSCAL JSON)
• List in-scope components: hostnames, instance groups, container workloads, images, AMIs, appliance models, or Kubernetes namespaces that implement that mechanism.

Deliverable: a one-page scope statement owned by an engineering leader and approved by GRC.

2) Identify all potential persistent write paths

Build a threat-informed inventory for the component:

• Filesystems and mount points (root, /etc, /var, /opt)
• Local package installs and patching flows
• Local users/SSH authorized_keys
• Scheduled jobs (cron/systemd timers/task scheduler)
• Local logs, audit trails, crash dumps
• Local secrets and tokens
• “Stateful” agents (EDR, config management, monitoring) that write locally

Deliverable: a “persistent write path register” with disposition for each path: eliminate, make read-only, make ephemeral, or justify out of scope.

3) Implement immutability controls that satisfy SC-34(1)

Pick the pattern that fits your platform, then document it.

Common acceptable patterns (choose what matches your environment):

• Immutable image + replace, don’t patch: All changes go through CI/CD to build a new image. Runtime instances cannot be modified in a way that persists after restart.
• Read-only root filesystem: Configure the component so the OS/application partitions are mounted read-only; only ephemeral mounts exist for runtime needs.
• Ephemeral runtime storage: Use tmpfs/ephemeral disks that are cleared on reboot for any necessary write activity.
• Externalize state: Send logs to a centralized logging service; store configuration in a secure, versioned config system; store secrets in a secrets manager. The component itself should not keep persistent writable state.

You do not need every pattern. You need a coherent story, technically enforced, that removes persistence across restart for writable paths in the component implementing SC-34. (NIST SP 800-53 Rev. 5 OSCAL JSON)

4) Lock down operations so people can’t reintroduce persistence

This is where programs fail in audits: the design is good, but operations bypass it.

• Change control: Require changes to flow through code review and pipeline approvals for any image/build/config artifacts tied to the SC-34 component.
• Privileged access: Restrict interactive admin access; if you must allow break-glass, ensure post-incident rebuild/replace restores a known-good immutable state.
• Configuration drift detection: Detect and alert on changes to files that should never persist.

Deliverable: a runbook that states how updates happen and how emergency access is handled without creating persistent writable storage.

5) Validate with tests that map directly to the requirement

Design tests that an assessor can understand:

• Attempt to write a file in candidate locations.
• Restart the component (or power cycle in lab conditions).
• Verify the write does not persist.

Record the commands, results, and the environment identifiers (image hash/version). Keep this as recurring evidence, not a one-time screenshot. (NIST SP 800-53 Rev. 5)

Required evidence and artifacts to retain

Maintain a lightweight evidence set that connects design to operation:

• Control implementation statement for SC-34 and SC-34(1) that names the ODP mechanism and in-scope components. (NIST SP 800-53 Rev. 5 OSCAL JSON)
• Architecture diagram showing where state, logs, and configuration live (and that local persistence is blocked).
• System hardening/config exports proving read-only mounts or immutable settings (mount configuration, container security context, image build config).
• CI/CD build artifacts: image hashes, signed builds (if used), pipeline logs showing controlled releases.
• Validation test report: “write, restart, verify non-persistence” with timestamped outputs.
• Operational runbooks: patching via replacement, break-glass procedure, incident recovery steps.
• Exception register (if any): explicit risk acceptance, scope boundaries, compensating controls, and expiration/review trigger.

Practical note: Daydream is helpful here as a control system of record. Store the SC-34(1) scope statement, owner assignment, and the exact recurring evidence list so audits don’t turn into a scavenger hunt.

Common exam/audit questions and hangups

Expect these lines of questioning:

1. “What is the sc-34.01_odp mechanism in your environment?” If you cannot name it plainly, you will struggle to prove compliance. (NIST SP 800-53 Rev. 5 OSCAL JSON)
2. “Show me that nothing writable persists across reboot.” Auditors often pick a path you didn’t think about (logs, temp directories mapped to persistent volumes, local config overrides).
3. “How do you patch?” If your process involves in-place modification of a running instance, you need to show that changes do not survive restart or that the instance is replaced from a known-good image.
4. “What about exceptions?” If any persistent writable storage exists, you need a documented exception with explicit scope and compensating rationale.

Frequent implementation mistakes (and how to avoid them)

Mistake	Why it fails SC-34(1)	How to avoid
Leaving a persistent volume attached “just for logs”	Logs become a durable write path; attackers can plant or tamper with artifacts	Centralize logs externally; keep only ephemeral local buffers
Immutable base image, but mutable config stored on disk	Config drift persists across reboot	Store config in a controlled external system; mount read-only at runtime
“Read-only root” but writable /var on persistent disk	/var often contains service state that persists	Make /var ephemeral or tightly scoped and proven non-persistent for the component
Break-glass SSH becomes normal ops	Interactive changes create undocumented persistence	Enforce rebuild/replace after break-glass and collect evidence of restoration
No test evidence	Assessors cannot confirm the enhancement is met	Add a simple restart persistence test to release gating

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. (NIST SP 800-53 Rev. 5 OSCAL JSON)

Risk-wise, SC-34(1) reduces the chance that a compromise survives a restart and limits the ability of an attacker to establish durable footholds through local state. That maps directly to operational resilience: the system returns to a known baseline after reboot when implemented correctly. (NIST SP 800-53 Rev. 5)

A practical 30/60/90-day execution plan

First 30 days (scope + design decisions)

• Assign a control owner for SC-34(1) and identify the sc-34.01_odp mechanism in plain language. (NIST SP 800-53 Rev. 5 OSCAL JSON)
• Produce the in-scope component list and the persistent write path register.
• Decide on the implementation pattern (immutable images, read-only filesystem, ephemeral storage, externalized state).
• Draft evidence requirements and create an audit-ready folder structure (or a Daydream control page) for recurring artifacts.

Days 31–60 (implementation + operational controls)

• Implement the selected pattern on a pilot component.
• Update runbooks: patching via replacement, break-glass handling, drift detection expectations.
• Add build/pipeline guardrails so engineers cannot casually introduce persistent storage.
• Start generating evidence on a cadence tied to releases (build logs, configuration exports, versioned diagrams).

Days 61–90 (validation + expansion + assessment readiness)

• Run and document the “write, restart, verify non-persistence” test for each component class.
• Expand to remaining in-scope components and standardize the approach.
• Hold an internal “mock interview” where GRC asks the audit questions above and engineering responds with the evidence set.
• Finalize any exceptions with explicit boundaries and a planned remediation path.

Frequently Asked Questions

Does SC-34(1) mean the entire system must be stateless?

No. It applies to the component(s) where you employ the sc-34.01_odp mechanism, and the requirement is that those components have no persistent writable storage across restart or power cycles. Document scope clearly so assessors know what is in and out. (NIST SP 800-53 Rev. 5 OSCAL JSON)

Can I store logs locally if I rotate them?

Rotation does not fix persistence. If logs survive restart on writable storage, they are a persistent write path. Send logs to a centralized logging service and keep only ephemeral local buffering if required.

What counts as “persistent across component restart” in cloud environments?

Anything that remains after the instance/container restarts within your architecture for that component (for example, attached volumes, durable disks, or host paths mapped to persistent storage). Your test should simulate the restart and verify the data does not survive.

If my component needs to write temporary files, am I blocked?

No. You can allow writes to ephemeral storage that is cleared on restart. The evidence should show which directories are writable and why they do not persist.

How do I handle emergency production fixes without violating SC-34(1)?

Use break-glass only for stabilization, then rebuild/replace from an approved image so the final state after restart contains no persistent writes made during the incident. Keep the incident record and replacement proof with your SC-34(1) evidence.

What is the minimum evidence an auditor will accept?

A scoped control statement naming the sc-34.01_odp mechanism, configuration proof that persistent writes are blocked, and a repeatable test showing writes do not survive restart. Store these artifacts in a system that preserves version history and ownership. (NIST SP 800-53 Rev. 5 OSCAL JSON)