AC-3(6): Protection of User and System Information

AC-3(6): Protection of User and System Information requires you to prevent users (and their processes) from accessing, copying, or exfiltrating other users’ information or sensitive system information unless explicitly authorized. Operationalize it by defining what “user information” and “system information” mean in your environment, then enforcing separation and access restrictions at the OS, application, database, and logging layers with testable evidence. ¹

Key takeaways:

• Define and classify “user information” and “system information” so your access rules can be tested, not debated. ¹
• Enforce technical separation controls (least privilege, isolation boundaries, and controlled information flows) across platforms, not only in policy. ¹
• Build audit-ready evidence: configs, access reviews, and proof of negative testing (blocked access) tied to the control owner and procedure. ²

AC-3 is the NIST 800-53 Access Enforcement control family; enhancement (6) focuses on protecting user and system information from unauthorized access that can occur even when a user is “validly logged in.” The practical problem is common: multi-tenant apps, shared admin tooling, broad read permissions in databases, overly permissive logs, and support workflows that accidentally expose other users’ data or sensitive system details (like configs, secrets, or security telemetry).

For a Compliance Officer, CCO, or GRC lead, the fastest way to make AC-3(6) real is to treat it as a set of enforceable boundaries: (1) what categories of information must be protected, (2) which roles may access each category, (3) where that information resides, and (4) which technical controls prove the boundary exists. Your goal is simple: demonstrate that a user cannot access information outside their authorization, and that the system does not disclose sensitive system information through interfaces, logs, error messages, or administrative channels without explicit permission. ¹

Regulatory text

Control excerpt: “NIST SP 800-53 control AC-3.6.” ²

What this means for operators: AC-3(6) is an access enforcement enhancement under AC-3. You must implement controls that protect (a) user information and (b) system information from unauthorized access. In practice, auditors expect to see technical enforcement (not only policy) that prevents cross-user access, prevents inappropriate disclosure of system details, and provides evidence the protections operate as designed. ¹

Plain-English interpretation (what you’re on the hook for)

You need to ensure that authenticated access does not equal authorized access to:

• Other users’ information (cross-tenant or cross-account exposure, “horizontal privilege escalation,” shared storage exposure).
• Sensitive system information (configuration, secrets, detailed system state, security tooling output, debug traces, privileged logs).

A clean test: pick a normal user, attempt to retrieve another user’s records and attempt to retrieve sensitive system info via UI, API, CLI, logs, and support channels. The system should deny, redact, or strictly gate access based on role and need-to-know. ¹

Who it applies to

Entity types

• Federal information systems.
• Contractor systems handling federal data. ¹

Operational contexts where AC-3(6) becomes “high friction”

• Multi-tenant SaaS (tenant isolation failures).
• Shared platforms (Kubernetes clusters, shared VDI/jump hosts).
• Centralized logging/SIEM and support tooling (logs and tickets become a disclosure channel).
• Data lakes/analytics warehouses where broad read access is common.
• Third-party access paths (MSPs, support vendors, consultants) where “temporary access” becomes permanent.

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

Step 1: Name the control owner and define scope (so it’s executable)

• Assign one accountable owner (often IAM, Security Engineering, or Platform Security) and identify implementation partners (AppSec, Data Platform, SRE, Support Ops).
• Document in-scope systems (apps, APIs, databases, logging stacks) and in-scope information types (user data classes; system data classes).
  Deliverable: a one-page control implementation procedure and ownership map. ²

Step 2: Define “user information” and “system information” for your environment

Create a short classification table you can test against:

Category	Examples (edit for your environment)	Typical allowed roles
User information	customer records, files, messages, billing data, tokens tied to a user	user (own only), support (scoped), admins (break-glass)
System information	system configs, infrastructure metadata, debug traces, detailed errors, security logs	SRE/SecOps, limited admins

Key requirement: these definitions must map to where the data actually lives (tables, buckets, indices, log streams). ¹

Step 3: Implement access enforcement at every layer where disclosure can occur

Focus on “defense in depth” enforcement points auditors can validate:

1. Application and API authorization

• Enforce object-level authorization (records belong to a user/tenant; access checked every request).
• Deny-by-default for new endpoints and new object types.
• Prevent IDOR patterns (insecure direct object references) by checking ownership and role every time.

2. Database and storage controls

• Restrict broad read roles; separate read paths for support vs engineering vs analytics.
• Segment tenant data logically (row-level security / tenant_id checks) or physically where required by risk.
• Ensure backups and exports are access controlled; exports are a frequent blind spot.

3. System information exposure controls

• Redact secrets from logs.
• Configure error handling to avoid disclosing stack traces or system internals to non-privileged users.
• Restrict access to admin consoles and observability tools (APM, logs, tracing) to least privilege.

4. Privileged access and support workflows

• Require ticket-based approval for “view customer data” actions where feasible.
• Record and review privileged sessions (or at minimum, log access events with who/what/when).
• Use break-glass accounts sparingly; restrict and monitor.

5. Third-party access paths

• Ensure third parties use unique identities and scoped roles.
• Time-bound access where possible and review access grants on a defined cadence.

Auditor mindset: if it’s possible to fetch it, it must be governed. ¹

Step 4: Test the control with “prove it fails closed” checks

Create repeatable tests that generate evidence:

• Attempt cross-user access via API by swapping identifiers.
• Attempt cross-tenant access via UI deep links.
• Attempt access to sensitive logs or debug endpoints as a non-privileged role.
• Validate that denied access is logged appropriately (without leaking sensitive system details in the log message).

Capture screenshots, request/response samples (sanitized), and test case results. ¹

Step 5: Make it auditable (mapping, procedure, recurring artifacts)

This is where programs stall: the technical work exists, but nobody can show it cleanly.

• Maintain a control narrative: “what protects what, where, and who approves changes.”
• Tie recurring evidence to a calendar: access reviews, privileged access reports, and config baselines.
• If you use Daydream, treat it as the system of record to map AC-3(6) to the control owner, implementation procedure, and recurring evidence artifacts so assessment requests don’t turn into a scavenger hunt. ²

Required evidence and artifacts to retain

Keep evidence that answers: “What stops unauthorized access?” and “How do you know it works?”

Core artifacts

• Control narrative and scope statement for AC-3(6). ¹
• Data classification mapping for “user information” and “system information.” ¹
• Role/permission matrix (RBAC/ABAC) including privileged and support roles. ¹
• Configuration evidence: IAM policies, database grants, storage ACLs, tenant isolation controls, logging redaction settings. ¹
• Test evidence: negative tests showing blocked cross-user and blocked system-info disclosure. ¹
• Access review outputs and exceptions (who approved, why, expiry). ¹

Common exam/audit questions and hangups

What auditors ask

• “Show me how a normal user is prevented from accessing another user’s data.” ¹
• “Where is system information exposed, and how is it restricted?” (logs, admin UIs, debug endpoints). ¹
• “Prove that controls work: show a failed access attempt and the log trail.” ¹
• “How do you control support and third-party access to customer data?” ¹
• “What’s the change process for authorization logic and permission policies?” ¹

Where teams get stuck

• “System information” is undefined, so the scope expands mid-audit.
• Authorization checks are inconsistent across services.
• Logs contain sensitive data and are broadly accessible.

Frequent implementation mistakes (and how to avoid them)

1. Relying on UI controls without API enforcement
   Fix: enforce authorization in the API/service layer; treat UI as untrusted. ¹

2. Assuming IAM role assignment equals least privilege
   Fix: validate permissions by testing real access paths and reviewing effective permissions. ¹

3. Overlooking observability as a disclosure channel
   Fix: restrict log access, redact sensitive fields, and limit debug endpoints in production. ¹

4. Support “God mode” with no traceability
   Fix: require scoped tools, approvals, and logging for customer-data access by support and third parties. ¹

5. No durable evidence
   Fix: define recurring artifacts up front (configs, reviews, tests) and store them centrally. Daydream helps by keeping the mapping between AC-3(6), owners, and evidence consistent across audit cycles. ²

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so treat enforcement expectations as assessment-driven: federal ATO processes, customer security reviews, and independent assessments commonly test access control failures by attempting cross-user access and inspecting logs, admin tools, and support workflows. The risk is direct: unauthorized disclosure of customer data, credential material in logs, and attacker lateral movement through over-broad read access. ¹

A practical 30/60/90-day execution plan

First 30 days (stabilize scope and visibility)

• Assign owner, define in-scope systems, and publish your “user vs system information” definitions. ¹
• Inventory access paths: UI, API, database, storage, logs, admin tools, support tooling. ¹
• Identify top exposure points: shared logs, shared admin accounts, broad database read roles. ¹

Days 31–60 (enforce and prove)

• Implement or tighten object-level authorization checks in high-risk services. ¹
• Restrict access to observability and admin tools; add redaction for sensitive fields in logs. ¹
• Write and run negative tests; store results as evidence. ¹

Days 61–90 (operationalize and make it repeatable)

• Stand up recurring access reviews for privileged roles and third-party roles; track exceptions. ¹
• Add change controls for permission policy changes and authorization logic changes. ¹
• Centralize evidence and mapping (owner, procedure, artifacts) in Daydream so audits pull from a single record. ²

Frequently Asked Questions

Does AC-3(6) require encryption?

AC-3(6) is an access enforcement requirement focused on preventing unauthorized access to user and system information. Encryption can support the outcome, but you still need authorization controls that prevent cross-user and sensitive system-info access. ¹

What counts as “system information” in practice?

Treat it as information that reveals how the system works or is secured, such as detailed configs, privileged logs, debug traces, and security telemetry. Define it explicitly and map it to concrete repositories (log indices, admin consoles, config stores). ¹

How do we show evidence that access is blocked?

Keep negative test results: attempted cross-user access requests, denial responses, and corresponding audit logs (sanitized). Auditors want proof of enforcement, not only design diagrams. ¹

We’re multi-tenant. Is tenant isolation enough to satisfy AC-3(6)?

Tenant isolation is a primary mechanism, but auditors will still look for object-level authorization and least-privilege access to shared components like logs, admin tooling, and data warehouses. Document where isolation is enforced and how you test it. ¹

How should we handle support engineers who need to view customer data?

Create scoped support roles, require approvals for sensitive access, and log support access to customer records. Tie support access back to tickets and keep reviewable records. ¹

What’s the minimum documentation that keeps AC-3(6) from becoming an audit fire drill?

A control narrative with owner, scope, and enforcement points; a role/permission matrix; and a recurring evidence list (config snapshots, access reviews, negative tests). Daydream helps maintain the mapping and evidence set across cycles. ²

Footnotes

1. NIST SP 800-53 Rev. 5

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