SC-34(2): Integrity Protection on Read-only Media

Read-only media still shows up in modern environments: immutable/WORM storage, write-once logs, firmware images distributed on physical media, gold images, offline backups, incident response evidence kits, and “break-glass” recovery media. SC-34(2) is narrowly framed but operationally tricky because it spans two moments in time: the integrity of information before it becomes immutable, and the control of the media after the write event.

For a CCO, GRC lead, or Compliance Officer, the fastest path to operationalize SC-34(2) is to treat it like a controlled release process plus a media custody process. First, you standardize how content is built, approved, and integrity-checked prior to writing. Second, you standardize how the media is labeled, inventoried, stored, moved, accessed, and destroyed (or archived) after it becomes read-only. If you do only the first half (hashes) and ignore the second half (custody), you fail the intent. If you do only custody controls without integrity checks, you risk permanently recording corrupted or malicious content.

This page gives requirement-level guidance you can hand to IT Ops, Security Engineering, or a third party that produces or stores your read-only media, and then collect clean evidence for assessments mapped to NIST SP 800-53 Rev. 5. ¹

Regulatory text

Requirement (verbatim): “Protect the integrity of information prior to storage on read-only media and control the media after such information has been recorded onto the media.” ²

Operator interpretation:
You must implement two linked control objectives:

1. Pre-write integrity protection: Before data is written to read-only media, you have to protect it from unauthorized modification and confirm it is exactly the approved content (for example, using hashes, digital signatures, controlled build pipelines, and approvals).
2. Post-write media control: After the write, you must control the physical or logical media so the recorded content cannot be substituted, tampered with, mishandled, or accessed outside authorization.

This is a “point of no return” control. If the content is wrong at write time, read-only media preserves the problem. If custody is weak after writing, attackers or careless handling can invalidate the trust you placed in immutability.

Plain-English interpretation (what SC-34(2) is really asking)

SC-34(2) expects you to answer three questions with evidence:

• How do you know the bytes you wrote were the approved bytes? (integrity checks + approvals)
• Who had access to the media and when? (custody + access control)
• Can you detect and respond to tampering or substitution? (inventory reconciliation + seals + logging + periodic checks)

If your environment uses logical read-only media (for example, WORM/object lock), treat it the same way: integrity before “locking,” and strict control of the storage location, permissions, and lifecycle after locking.

Who it applies to (entity and operational context)

Entity types:

• Federal information systems and contractors handling federal data (including regulated environments inheriting NIST SP 800-53 requirements through contracts, ATO packages, or customer security addenda). ¹

Operational contexts where auditors expect SC-34(2) to be addressed:

• Offline backups written to read-only formats or stored as immutable archives
• Incident response evidence written to read-only media for preservation
• Distribution of firmware, boot media, “gold images,” or recovery media
• Compliance archives intended to be non-rewritable (WORM storage or equivalent)
• Any third party that manufactures, duplicates, stores, transports, or destroys your read-only media

Control owner (typical): Information Security or IT Operations, with Records Management and Physical Security support. If a third party handles media duplication or storage, vendor management should be part of the control design.

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

Step 1: Define scope and “read-only media” in your environment

• List every use case where you write to read-only media (physical discs, write-protected USBs, tape, WORM/object lock, immutable snapshots that meet your definition).
• Assign each use case an owner, system boundary, and data classification.
• Decide what “control after writing” means per use case (on-prem vault, secure cabinet, offsite storage provider, locked bucket with limited principals).

Deliverable: scoped inventory of read-only media workflows.

Step 2: Implement a pre-write integrity gate

Build a standard checklist that must be satisfied before writing occurs:

• Source control / provenance: identify authoritative source of the data (build artifact repository, case management export, backup job output).
• Approval: require an approver for the content to be written (release manager, incident commander, records officer).
• Integrity mechanism: generate a cryptographic hash and/or digital signature for the final artifact set, store it in a tamper-evident system (ticket, CMDB record, signed manifest).
• Write authorization: only approved roles can perform the write/burn/lock action.

Practical example: For an incident evidence package, create an “evidence manifest” that includes file list, hash values, case ID, approver, and the exact media identifier that will receive the write.

Step 3: Perform the write, then immediately verify

• Record who performed the write, from which workstation, and when.
• After writing, re-read the media (or validate immutable object checks) and confirm the hashes/signatures match the pre-write manifest.
• If verification fails, treat the media as nonconforming and quarantine it.

Deliverable: write record + post-write verification record tied to the same ticket/change.

Step 4: Control the media after writing (custody + protection)

Implement controls proportional to sensitivity and threat model:

• Unique identification: label media with a unique ID; avoid sensitive content labels on the outside.
• Inventory and reconciliation: maintain an inventory register; reconcile on a defined cadence aligned to your risk.
• Physical security: locked storage, restricted access, visitor logging where relevant.
• Chain of custody: require sign-in/sign-out for removal from storage; record transfers to offsite storage or a third party.
• Transport controls: tamper-evident bags, approved couriers, documented handoffs for high-sensitivity media.
• Access control for logical WORM: restrict principals that can place objects into immutable state; restrict who can read/download; alert on permission changes.
• Environmental controls: protect from damage if availability matters (fire/water), aligned to BCP/DR expectations.

Note: “Control the media” includes preventing substitution. If two discs look identical and your process can’t prove which one is the official copy, auditors will challenge integrity.

Step 5: Manage lifecycle: retention, re-issuance, and destruction

• Define retention periods and storage locations based on records requirements and contracts.
• For re-issuance (making additional copies), repeat pre-write integrity and verification steps; treat duplication as a new write event.
• For destruction/disposition, document method, approval, and completion; update inventory to show final status.

Step 6: Extend the control to third parties

If a third party stores, transports, or duplicates read-only media:

• Put handling and chain-of-custody requirements in the contract/SOW.
• Require evidence: inventory logs, custody records, incident notification, and access controls.
• Test the third party process during audits with sample pull requests (request a specific media ID’s custody trail).

Step 7: Make it auditable (map, evidence, cadence)

Operationalize with a one-page control procedure:

• scope, roles, tools, required logs, required approvals, exception handling, and review cadence.
• Map SC-34(2) to your internal control library with a named owner and recurring evidence set. ²

If you use Daydream to manage control ownership and evidence collection, treat SC-34(2) as an evidence-backed workflow: assign tasks to artifact owners (release, IR, backup), collect manifests and custody records on schedule, and keep them assessment-ready without rebuilding the story each audit cycle.

Required evidence and artifacts to retain

Keep evidence that proves both pre-write integrity and post-write control:

Pre-write integrity

• Approved request/ticket or change record authorizing the write
• Hash/signature manifest for the dataset prior to writing
• Access logs showing only authorized roles prepared the content
• Build/export logs that show provenance of the data

Write + verify

• Record of the write event (operator, device, timestamp, media ID)
• Post-write verification results (re-read + hash match)
• Exception records for failures and remediation steps

Post-write media control

• Media inventory register (unique ID, location, status, owner)
• Chain-of-custody logs (check-in/check-out, transfers, transport)
• Storage access logs (physical access roster or system access logs for logical WORM)
• Retention and destruction approvals + destruction certificates where applicable

Common exam/audit questions and hangups

• “Show me how you verify integrity before writing to read-only media.” Auditors will want the manifest created before the write.
• “How do you prove the media in the vault is the same media referenced in the ticket?” Weak labeling and no custody trail is a common hangup.
• “Who can create immutable objects / burn media / produce copies?” Overbroad permissions fails the “control” intent.
• “How do you handle re-issuance or duplication?” Many teams forget that copying is another integrity-critical event.
• “What happens when verification fails?” If you can’t show quarantine and investigation steps, integrity claims look theoretical.

Frequent implementation mistakes and how to avoid them

1. Hashing after the write only.
   Fix: generate and approve the manifest before writing; then verify after writing against the pre-write manifest.

2. No unique media identifiers.
   Fix: assign a media ID and reference it everywhere (ticket, manifest, custody log).

3. Treating immutable storage as “set and forget.”
   Fix: control admin permissions, monitor policy changes, and retain logs for lock actions and permission changes.

4. Third party custody ignored.
   Fix: require chain-of-custody evidence contractually and sample-test it during due diligence and renewals.

5. Evidence scattered across email.
   Fix: centralize in your GRC system or case tooling; require attachments/links as part of closeout criteria.

Enforcement context and risk implications

No public enforcement cases were provided for this requirement in the supplied sources, so this page does not cite enforcement outcomes.

Operational risk is straightforward: once malicious or incorrect content is written to read-only media, your recovery media, compliance archive, or evidentiary record can become untrustworthy. Weak custody controls create opportunities for substitution, unauthorized disclosure, and audit failure due to inability to prove authenticity. ¹

A practical 30/60/90-day execution plan

First 30 days (Immediate)

• Identify all read-only media use cases and owners.
• Pick one standard integrity method (hash manifest format, signature approach) and one custody log approach.
• Draft the SOP: pre-write approval, manifest creation, write, post-write verification, custody handling, exceptions.

By 60 days (Near-term)

• Implement the workflow in tickets/change management (required fields: media ID, approver, manifest link, verification result).
• Stand up a controlled inventory register and chain-of-custody template (physical and/or logical).
• Train the operators who perform writes and the staff who manage storage/offsite transfers.

By 90 days (Operationalize and test)

• Run a tabletop or sample-based internal audit: pick several media items and reconstruct the chain from approval to storage.
• Fix gaps in logs, labeling, and permissioning.
• Add recurring evidence tasks in your GRC program so SC-34(2) artifacts are collected continuously rather than during audits. Daydream fits well here because it can assign owners and track recurring evidence for manifests, custody logs, and verification records across teams.

Frequently Asked Questions

Does SC-34(2) apply if we don’t use physical discs and only use immutable cloud storage?

Yes, if you treat that storage as “read-only media” in your implementation. You still need integrity checks before locking content and strong controls over who can lock, read, or change retention settings. ¹

What’s the minimum acceptable integrity check before writing?

The requirement does not mandate a specific mechanism. In practice, a cryptographic hash manifest created and approved before the write, then verified after the write, is a common and auditable pattern. ²

If the media is read-only, why do we need to “control the media” after writing?

Read-only does not stop loss, theft, substitution, or unauthorized disclosure. Post-write controls prove the media stayed in authorized custody and that the recorded content remained trustworthy. ²

How do we handle duplication of read-only media (making additional copies)?

Treat duplication as a new write event. Require approval, generate or re-validate the manifest, perform post-write verification, and log custody for the new media IDs.

What evidence is most often missing during assessments?

Teams often lack a pre-write manifest with approval, and they can’t produce a complete chain-of-custody trail linking the specific media ID to a controlled location over time.

Can a third party store our read-only media and still meet SC-34(2)?

Yes, if you impose custody, access, logging, and incident notification requirements contractually and you can obtain evidence on demand. Your assessors will still expect you to demonstrate oversight and traceability.

Footnotes

1. NIST SP 800-53 Rev. 5

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