AC-3(5): Security-relevant Information

AC-3(5) requires you to block all access to security-relevant information except when the system is in a secure, non-operable state (for example, during controlled maintenance or forensic handling). To operationalize it fast, you must define what “security-relevant information” is for your environment, identify where it lives, and implement technical and procedural controls that prevent access during normal operations. ¹

Key takeaways:

• Define and scope “security-relevant information” (logs, audit configs, alerts, authZ rules, key materials, sensor outputs) for each system boundary.
• Enforce “access only in secure, non-operable states” with tested runbooks plus technical gates (break-glass, maintenance modes, network isolation, read-only mounts).
• Keep assessor-ready evidence: data inventory, access rules, change records, logs, and proof that non-operable state controls work.

The ac-3(5): security-relevant information requirement is easy to misunderstand because it is not “just another least privilege control.” The intent is to stop adversaries, insiders, and even routine admins from accessing or manipulating the information that makes security controls trustworthy while the system is operating normally. If an attacker can read or change security-relevant information during normal operations, they can hide activity, disable detection, tamper with audit trails, or pre-stage persistence.

Operationally, AC-3(5) forces a clear separation between (1) day-to-day system operation and (2) rare, tightly controlled conditions where security-relevant information can be accessed. That separation is usually achieved through a combination of system state controls (maintenance mode, offline imaging, isolated admin plane), privileged access management, and strong procedures that require the system to be in a secure, non-operable state before access is granted.

This page gives requirement-level guidance a Compliance Officer, CCO, or GRC lead can hand to engineering: what to define, what to build, what to test, and what evidence to retain for an assessment mapped to NIST SP 800-53 Rev. 5. ²

Regulatory text

NIST requirement (excerpt): “Prevent access to {{ insert: param, ac-03.05_odp }} except during secure, non-operable system states.” ¹

What the operator must do:

1. Identify the category of information in your environment that qualifies as “security-relevant information” for AC-3(5).
2. Implement controls that prevent access to that information during normal system operations.
3. Allow access only when the system is in a secure, non-operable state, and define what qualifies as such a state for each system. ¹

Practical translation: if your SIEM rules, audit logs, EDR telemetry, IAM authorization policies, or similar artifacts can be accessed during normal operations, you need to add gates so access only occurs under controlled conditions that reduce tampering risk.

Plain-English interpretation (what AC-3(5) is really asking)

AC-3(5) is about protecting the “security truth” of the system: the data and configurations used to detect, investigate, and prove what happened. If that truth is accessible during normal operations, a malicious actor can:

• Delete or alter logs before they are forwarded.
• Modify alerting rules to suppress detection.
• Change audit configurations to stop recording.
• Exfiltrate sensitive security telemetry that reveals defensive coverage.

Your goal is to make access to that class of information rare, deliberate, and observable, and to tie it to a system condition where tampering is materially harder.

Who it applies to (entity and operational context)

AC-3(5) is commonly applied in:

• Federal information systems assessed against NIST SP 800-53. ²
• Contractor systems handling federal data where NIST SP 800-53 is in scope through contract requirements or an agency ATO boundary. ²

Operational contexts where this control gets real scrutiny:

• Systems supporting incident detection and response (logging pipelines, SIEM, EDR management planes).
• Identity and access systems (directories, policy engines, authorization services).
• Platforms where admins have broad access by default (shared UNIX fleets, legacy hypervisors, flat networks).
• Environments with frequent break-fix and “temporary admin” patterns.

Define your scope: what counts as “security-relevant information”

The control text uses an organization-defined parameter. You must decide and document what it includes for each system boundary. ¹

Use this scoping checklist and treat it as your minimum starting set:

Category	Examples (adapt to your stack)	Why it matters
Audit records and log data	OS logs, app logs, cloud audit logs, database audit trails	Used for detection and investigation; tampering destroys accountability
Audit/logging configuration	Auditd rules, agent configs, log routing, parsing rules	An attacker can disable or degrade visibility
Detection content	SIEM rules, correlation logic, alert thresholds, suppression lists	Quietly blinds security monitoring
Security tooling telemetry	EDR event streams, sensor outputs, vulnerability scan results	Reveals defensive posture; can be altered to mislead
IAM and authorization control data	Authorization policies, group mappings, privileged role definitions	Enables privilege escalation or persistence
Cryptographic/security control materials	Key material locations, HSM admin states, KMS policy configs	Impacts confidentiality and integrity controls

Decision rule to document: If changing or viewing the information could reasonably weaken detection, response, or accountability, treat it as security-relevant under AC-3(5).

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

1) Assign a control owner and write an implementation procedure

Pick one accountable owner (usually Security Engineering or Platform Security) and one GRC owner for evidence quality. Build a short procedure that an assessor can follow end-to-end, including how the secure, non-operable state is invoked and approved. ¹

Daydream tip: Track AC-3(5) as a discrete control with an owner, implementation narrative, and recurring evidence tasks so you do not “re-discover” the same decisions every audit cycle.

2) Create an inventory of security-relevant information stores and paths

For each in-scope system, list:

• Where security-relevant information is stored (hosts, cloud services, buckets, log indices).
• How it flows (agents, forwarders, pipelines).
• Who can access it today (roles, groups, service accounts).
• Which access paths are “normal operations” vs “non-operable state.”

This inventory becomes your primary scoping artifact for AC-3(5).

3) Define “secure, non-operable system state” per system type

You need a definition that engineering can implement and audit can test. Examples you can adapt:

• Offline / powered-down: system is shut down and storage is mounted read-only on a forensic workstation.
• Maintenance mode with isolation: production traffic disabled, admin plane restricted to a hardened jump host, and network egress blocked except required management endpoints.
• Immutable snapshot review: access only via approved snapshots or replicated log stores that production cannot modify.

Write the definition and the required preconditions (approvals, ticket, monitoring, time-bounded access).

4) Implement technical gates that enforce the state requirement

Common patterns that work in practice:

• Break-glass workflows with time-bound privileges and mandatory ticket references.
• Privileged Access Management (PAM) for admin sessions to logging and detection platforms.
• Network segmentation so security-relevant stores are unreachable from normal admin networks.
• Write-once / append-only logging and remote forwarding so production systems cannot alter the authoritative log copy.
• Separation of duties between operators of the production system and administrators of the logging/detection plane.

Your design target: normal admin access should not include direct read/write access to the authoritative security-relevant stores.

5) Add procedural controls for “rare access” events

Technical gates still need procedural rigor:

• Require a change/request ticket for any access event.
• Use a defined approval chain (system owner + security).
• Log and review each event (who, what, why, duration, commands or actions taken).
• Require post-access validation (for example, integrity checks, alerting rules verification).

6) Test the control the way an assessor will

Run two tests and retain the outputs:

• Negative test: confirm users cannot access the defined security-relevant information during normal operation.
• Positive test: confirm approved personnel can access it when the system is placed into the defined secure, non-operable state, and that all access is logged.

Required evidence and artifacts to retain

Keep evidence that proves design and operation:

• AC-3(5) scope statement defining “security-relevant information” for each boundary. ¹
• Inventory of repositories and access paths (data stores, services, indices, buckets, endpoints).
• Role and access mappings (RBAC exports, IAM policies, group membership snapshots).
• Runbooks for invoking the secure, non-operable state (maintenance mode / isolation / offline handling).
• Tickets and approvals for actual access events (change records, incident records).
• System logs showing attempted/denied access in normal operations and allowed access in non-operable states.
• Test records demonstrating both negative and positive tests, with date/time, tester, and results.

Common exam/audit questions and hangups

Expect these questions and prepare short answers with artifacts:

• “What exactly did you define as security-relevant information for this system?”
• “Show me how you prevent access during normal operations.”
• “What qualifies as a secure, non-operable state here, and who can declare it?”
• “Prove this is enforced technically, not just by policy.”
• “Show evidence from a real access event: approval, time-bound access, and logs.” ²

Hangups that stall assessments:

• Vague definitions (“security data” without listing repositories).
• Reliance on “only admins can access it” without state-based restriction.
• Lack of operational evidence (no tickets, no logs, no test outputs).

Frequent implementation mistakes (and how to avoid them)

1. Mistake: treating the SIEM UI as the only place to protect.
   Fix: include upstream components (agents, forwarders, pipelines, storage, rule repos).

2. Mistake: defining non-operable state but not enforcing it.
   Fix: enforce with network isolation, PAM, and conditional access controls tied to maintenance workflows.

3. Mistake: allowing production admins to modify security monitoring content ad hoc.
   Fix: move rules/config to version control with approvals, and restrict direct production edits.

4. Mistake: evidence gaps.
   Fix: schedule recurring exports/screenshots/log pulls and keep them in an audit repository mapped to AC-3(5). Daydream can track owners, procedures, and recurring artifacts so evidence stays current. ¹

Enforcement context and risk implications

No public enforcement cases were provided in the supplied source catalog for this specific enhancement, so do not treat it as tied to a particular regulator’s penalty posture. The risk is still concrete: if an attacker can access or alter security-relevant information during normal operations, you may lose incident detection, fail to reconstruct events, and be unable to prove control operation during an investigation or assessment. ²

A practical 30/60/90-day execution plan

First 30 days (stabilize scope and ownership)

• Assign control owner and GRC evidence owner.
• Draft the AC-3(5) scope statement for one priority system boundary.
• Inventory all repositories and access paths for that boundary.
• Define “secure, non-operable state” for that boundary and write the runbook.

Next 60 days (implement gates and workflows)

• Implement technical restrictions for normal operations (RBAC tightening, segmentation, PAM or break-glass).
• Add ticketing and approvals for access events.
• Centralize logs so the authoritative store is tamper-resistant from production.

By 90 days (prove operation and make it repeatable)

• Run negative and positive tests; retain evidence.
• Conduct one tabletop exercise where an engineer requests access and follows the workflow end-to-end.
• Establish recurring evidence collection and a quarterly control review cycle in your GRC system (Daydream or equivalent) mapped directly to AC-3(5). ¹

Frequently Asked Questions

What is “security-relevant information” in a cloud-native environment?

Start with cloud audit logs, IAM policies/role bindings, SIEM detection content, and the configuration for log routing and retention. If viewing or changing it could weaken detection or accountability, include it under AC-3(5). ¹

Does AC-3(5) mean nobody can read security logs during normal operations?

The control requires preventing access except in secure, non-operable states, so you should design for access via protected, authoritative copies and controlled workflows. Many teams meet the intent by separating “operational visibility” from “authoritative security-relevant stores” and tightly gating the latter. ¹

What counts as a “secure, non-operable system state” for SaaS?

You cannot power down SaaS, so define an equivalent state such as provider-supported maintenance modes, restricted admin-plane access from a hardened jump environment, and time-bound break-glass with documented approvals. Document your rationale and the compensating controls. ²

How do we show evidence if we rarely need to access this information?

Use test events: demonstrate that access is blocked during normal operations and allowed only under the defined non-operable state workflow. Retain the test ticket, approvals, and logs as operational evidence. ²

Can we satisfy AC-3(5) with policy only?

Expect assessors to look for technical enforcement plus logs showing the control operates. A policy can define scope and approvals, but it rarely proves prevention by itself. ¹

Who should own AC-3(5) in a typical enterprise?

Security Engineering or Platform Security usually owns implementation because it touches logging, IAM, and privileged access controls. GRC should own evidence quality and assessment readiness artifacts. ²

Footnotes

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

2. NIST SP 800-53 Rev. 5