AC-4(23): Modify Non-releasable Information

AC-4(23): modify non-releasable information requirement shows up when your environment has more than one “security domain” and information moves between them. “Security domain” can mean classified/unclassified, regulated/unregulated, production/non-production, tenant-to-tenant, or any segmentation where policy says content must not cross unchanged. The key is that the requirement is triggered by transfer between domains, not by storage within a domain.

For a Compliance Officer, CCO, or GRC lead, the fastest way to make this real is to focus on transfer choke points: email gateways, API gateways, file transfer services, cross-domain solutions, data pipelines, ticketing exports, and support tooling. If information flows around those choke points (ad hoc exports, shared drives, unmanaged SaaS connectors), you will struggle to prove you “modify non-releasable information” consistently.

This page gives requirement-level implementation guidance: what “modify” means in practice (redaction, tokenization, field suppression, downgrade/relabel), how to embed it into system design, what evidence auditors typically ask for, and how to execute without turning every transfer into a manual review. ¹

Regulatory text

Requirement excerpt: “When transferring information between different security domains, modify non-releasable information by implementing {{ insert: param, ac-04.23_odp }}.” ²

Operator interpretation of the text

• Trigger condition: Any time information is transferred between different security domains. ²
• Obligation: You must modify information that is non-releasable so it is no longer non-releasable before it crosses the boundary. ²
• Method: The control expects you to implement an organization-defined approach (“ac-04.23_odp”). Practically, that means your policy must name the approved modification methods and your systems must enforce them at transfer points. ²

“Modify” is intentionally broad. Your implementation can include redaction, masking, tokenization, field-level removal, downscoping attachments, stripping metadata, content transformation (for example, summary-only), or reformatting into an approved releasable template. The compliance test is whether non-releasable elements are prevented from crossing domains in their original form and whether enforcement is consistent.

Plain-English requirement

If data is allowed to move from Domain A to Domain B only after certain sensitive parts are removed or changed, you must:

1. define what counts as “non-releasable” for each boundary,
2. implement technical controls that apply the required modifications at the point of transfer, and
3. keep proof that transfers cannot bypass that modification step.

Who it applies to

Entity scope

• Federal information systems and contractor systems handling federal data implementing NIST SP 800-53 controls as part of an authorization, contract requirement, or internal control baseline. ¹

Operational scope (where it shows up)

• Cross-domain data movement: high-to-low networks, segmented enclaves, restricted VPC/VNETs, OT/IT bridges.
• Multi-tenant or environment splits: production to non-production, customer tenant to shared analytics.
• Third-party transfers: sending extracts to a processor, support platform exports, eDiscovery productions.
• Integration pathways: APIs, ETL/ELT pipelines, message buses, SFTP, email relays.

If your architecture has only one domain in practice, this control may be “not applicable,” but you still need to show you evaluated cross-domain transfers and confirmed there are no boundaries where releasability changes.

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

1) Identify “security domains” and map transfer paths

Build a boundary inventory that is usable by engineering and auditors:

• List each domain and its trust/releasability assumptions.
• Enumerate all cross-domain transfer mechanisms (tools, services, and human workflows).
• Record owners for each transfer mechanism (system owner and business owner).

Output: “Cross-Domain Transfer Register” (table) with domain pairs, transfer method, data types, and owner.

2) Define “non-releasable” by boundary, not by generic label

Create boundary-specific rules. Examples:

• “From restricted enclave to corporate SaaS: remove direct identifiers and secrets; strip file metadata.”
• “From production to dev: replace live customer fields with tokens; remove attachments.”

Avoid a single “non-releasable = PII” definition. Non-releasable may also include threat intel, keys, proprietary algorithms, vulnerability data, or classified markings depending on the domain relationship.

Output: “Releasability Matrix” that maps domain pair → prohibited elements → required modifications.

3) Choose the modification methods and make them testable

For each boundary rule, specify:

• Transformation method: redact, mask, tokenize, generalize, remove, summarize, reformat.
• Where it runs: gateway, broker, export job, middleware, CASB/DLP workflow, cross-domain solution.
• Failure behavior: block transfer, quarantine for review, or require approval with recorded justification.

Write rules so an assessor can test them. “Sensitive data must be protected” is not testable. “Outbound CSV exports must suppress columns X, Y, Z and replace account_id with token” is testable.

Output: “AC-4(23) Implementation Standard” (control procedure) that lists approved modification patterns and required enforcement points.

4) Implement technical enforcement at the choke points

Typical enforcement patterns:

• API gateway / service mesh: response filtering, schema-level field suppression, attribute-based release.
• ETL pipelines: irreversible tokenization before loading into lower-trust stores.
• Email/file gateways: attachment type restrictions, content inspection, metadata stripping, watermarking where appropriate.
• Cross-domain solutions: automated filters plus mandatory review for exceptions.

Design for “no bypass.” If engineers can export directly from the source domain to a destination domain without passing through the control, you will fail the spirit of AC-4(23).

Operational tip: require that every approved transfer path has a named control point (system and configuration reference) and a named log source for evidence.

5) Add exception handling that does not become a shadow pipeline

Define an exception process with:

• requester, approver, and approver criteria,
• time-bounded approval,
• required justification and compensating controls,
• mandatory logging of what was transferred and what modification was applied (or why not).

Aim to keep exceptions rare by making the standard transfer path easy.

6) Validate continuously with sampling and negative testing

You need proof the control works:

• Run periodic tests that attempt to transfer known non-releasable markers and verify the gate modifies or blocks them.
• Sample real transfers and verify transformations (for example, tokenization format, redacted fields).
• Verify logs show both the transfer attempt and the modification action.

If your modification is performed by a third party tool, include it in your monitoring and change control.

Required evidence and artifacts to retain

Keep artifacts that show design, enforcement, and operation:

Governance

• Cross-Domain Transfer Register (owned, current)
• Releasability Matrix (boundary-specific rules)
• AC-4(23) procedure/standard (methods, enforcement points, exceptions) ¹

Technical

• Configuration exports/screenshots for gateways/pipelines implementing modification rules
• Data transformation specs (schemas, field maps, tokenization design)
• Change records tying modifications to approved change management

Operational

• Logs showing transfers and applied modifications (or blocks/quarantines)
• Test results and sampling reports
• Exception tickets with approvals and expiration
• Evidence schedule: who reviews, how often, what they check

Assessment readiness

• Control mapping: control owner, implementing systems, and recurring evidence artifacts ²

Daydream fit: many teams lose time chasing “where do we prove this?” Daydream can track the owner, procedure, systems-in-scope, and the recurring evidence artifacts for AC-4(23) so evidence collection doesn’t depend on one engineer’s memory.

Common exam/audit questions and hangups

Assessors tend to probe the boundaries and bypass paths:

• “Show me all security domains and the approved cross-domain transfer paths.”
• “Where is ‘non-releasable’ defined, and who approves changes to that definition?”
• “Demonstrate a transfer where content was modified. Show the before/after and the log trail.”
• “What prevents an admin from exporting data directly from Domain A to Domain B?”
• “How do you test that the modification still works after updates?”

Hangup: teams often show a policy but cannot show enforcement at the specific transfer mechanism the auditor picks.

Frequent implementation mistakes and how to avoid them

1. Policy-only implementation.
   Fix: tie every boundary rule to a concrete enforcement point and a log source.

2. Overbroad “non-releasable” definitions that are impossible to implement.
   Fix: define boundary-specific prohibited elements and required transformations.

3. Manual review as the default control.
   Fix: automate modification for common flows; reserve manual steps for true exceptions.

4. Bypass through “convenience tools.”
   Fix: restrict direct exports, lock down service accounts, and require approved connectors.

5. No proof of modification.
   Fix: retain before/after test cases, transformation configs, and immutable logs.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement. Practically, AC-4(23) failures create:

• Data spill risk across enclaves, customers, or regulated environments.
• Authorization/ATO risk when assessors find ungoverned cross-domain pathways.
• Third-party risk if downstream recipients receive data that policy forbids you to release.

Even without a “fine,” this control can become a go/no-go gate in federal-aligned assessments because it speaks directly to preventing unauthorized information flow. ¹

Practical execution plan (30/60/90)

You asked for speed. Use phased execution without pretending every environment changes on a fixed calendar.

First 30 days (Immediate stabilization)

• Name the control owner and technical owners per transfer path.
• Build the Cross-Domain Transfer Register and identify the highest-risk pathways.
• Draft the Releasability Matrix for the top domain boundaries.
• Pick the enforcement approach for each boundary (gateway, pipeline, cross-domain solution) and document it in the AC-4(23) procedure. ²

By 60 days (Enforce and instrument)

• Implement modification rules at the primary choke points.
• Turn on logging that proves modification or blocking actions.
• Stand up exception workflow with approvals and expiry.
• Run initial validation tests with known non-releasable markers and retain results.

By 90 days (Prove repeatability)

• Expand coverage to secondary transfer mechanisms and less obvious pathways.
• Add recurring sampling and negative testing into GRC operations.
• Integrate evidence capture into your audit packet: register, matrix, configs, logs, tests, and exceptions.
• In Daydream, map AC-4(23) to the owners, implementation procedure, and recurring evidence so updates and reviews stay on schedule. ²

Frequently Asked Questions

What counts as a “security domain” for AC-4(23)?

Any environment boundary where policy changes what information is allowed to be released. Common domains are segmented networks, classified/unclassified enclaves, production/non-production, and restricted vs general SaaS destinations.

Does encryption satisfy “modify non-releasable information”?

Encryption protects confidentiality in transit, but it does not change the content’s releasability. AC-4(23) focuses on altering or removing the non-releasable elements before they cross the boundary. ²

Can we meet AC-4(23) with manual review before sending data?

Manual review can be part of an exception path, but auditors usually expect an enforced, repeatable control at the transfer mechanism. If the normal process is manual, you must show consistent criteria, approvals, and evidence that reviewers actually applied the required modifications.

How do we define “non-releasable” without boiling the ocean?

Start with the few boundary pairs that matter and define non-releasable as specific fields, data elements, and metadata that must be removed or transformed. Expand coverage after you have one boundary fully enforced and testable.

What evidence is most persuasive in an assessment?

A mapped list of transfer paths, a boundary-specific rule set, and technical proof: configuration showing the modification rule, plus logs and test cases showing a blocked or modified transfer. ¹

What if a third party system performs the modification (for example, a managed gateway)?

Treat the third party as part of your control boundary. Keep the contract/SOW language on processing, the configuration or attestation of the transformation behavior, and your own logs or monitoring that show transfers are routed through that service.

Footnotes

1. NIST SP 800-53 Rev. 5

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