SI-3(3): Non-privileged Users

SI-3(3): Non-privileged Users requires you to extend malware protection beyond admins and IT, so standard (non-privileged) users can’t bypass or disable anti-malware controls and their endpoints still receive effective, policy-enforced protection. Operationalize it by locking down endpoint protection settings, controlling exception handling, and keeping evidence that coverage and enforcement apply to non-admin accounts. ¹

Key takeaways:

• Treat non-privileged endpoints as first-class malware-protection scope, not “best effort.” ¹
• Your auditors will look for technical enforcement, not policy-only statements: tamper protection, enforced configs, and controlled exceptions.
• Evidence needs to prove ongoing operation for standard users: coverage, update posture, alerting, and exception approvals.

Most malware prevention programs accidentally overfit to the admin experience: IT can install tools, tune detections, and remediate incidents, but the real exposure sits with standard users clicking links, opening attachments, and running everyday software. SI-3(3): Non-privileged Users exists to close that gap by making sure malware defenses are not limited to privileged accounts or admin-managed workflows. ²

For a CCO or GRC lead, the fastest path is to translate SI-3(3) into three operator questions: (1) Are non-privileged user devices covered by the same anti-malware policy baseline as everyone else? (2) Can a standard user disable, uninstall, or meaningfully weaken protections? (3) Do we have a controlled process for exceptions and proof that it runs continuously? Your goal is not to “have an endpoint tool.” Your goal is to show enforced configuration, least-privilege-aligned controls, and measurable coverage for non-admin users across in-scope systems. ¹

This page gives requirement-level implementation guidance you can hand to endpoint engineering, security operations, and audit stakeholders, plus the evidence set you should retain for assessment readiness.

Regulatory text

Excerpt (as provided): “NIST SP 800-53 control SI-3.3.” ¹

What the operator must do: Implement and enforce malware protection in a way that covers non-privileged users and prevents standard users from bypassing or disabling protective capabilities on systems within scope of your NIST SP 800-53 program. Your implementation needs technical guardrails (not only policy language) and must generate repeatable evidence that protections apply to standard user contexts. ¹

Plain-English interpretation (what SI-3(3) is really asking)

SI-3(3): non-privileged users requirement means: standard users must be protected by anti-malware controls that remain effective even without admin rights, and your environment should not rely on users “doing the right thing” to stay protected. ¹

In practice, that usually translates to:

• Endpoint protection is centrally managed and applies to all user endpoints in scope.
• Tamper resistance is enabled so standard users can’t disable protection, stop services, or change security settings.
• Installation/removal rights are controlled; exception paths are limited and logged.
• Detections, quarantines, and remediation actions are monitored across the standard user fleet.

Who it applies to (entity and operational context)

Applies to:

• Federal information systems and contractor systems handling federal data where NIST SP 800-53 controls are in scope for the system boundary. ¹

Operationally, you should interpret “non-privileged users” as:

• Employees and contractors operating as standard users on corporate endpoints (laptops/desktops).
• Standard user sessions on shared systems (VDI, jump boxes configured for non-admin use, kiosks).
• Non-admin identities interacting with SaaS endpoints where local agents exist (managed endpoints) and with on-prem systems where malware protection is installed.

If your environment includes third parties (MSPs, software vendors, contractors) administering endpoints, SI-3(3) still applies: you must prove that non-privileged user devices under that third party’s management are protected and that exception handling is governed.

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

Use this as a build sheet for IT/SecOps, with GRC controlling scope and evidence.

1) Define the SI-3(3) scope boundary (systems + endpoint populations)

• Identify in-scope endpoints and user populations: corporate endpoints, VDI pools, servers with interactive user sessions, and any “non-admin workstation” categories.
• Document exclusions explicitly (for example, isolated lab systems) and require compensating controls and approval for each exclusion.

Deliverable: “SI-3(3) scope statement” tied to your system boundary and asset inventory.

2) Set a non-privileged-safe endpoint protection baseline

For your endpoint protection platform (EDR/AV):

• Enforce real-time protection and on-access scanning where applicable.
• Enforce automatic signature/engine updates.
• Enable tamper protection (prevent stop/uninstall/config edit by standard users).
• Lock local security UI/settings behind admin roles.
• Enforce cloud-delivered protection features your program approves.

Control intent: the standard user experience cannot meaningfully reduce protection.

Deliverable: Endpoint security baseline configuration (policy) mapped to SI-3(3).

3) Implement technical enforcement, not “policy-only”

Auditors typically separate “we have a policy” from “the endpoint won’t allow it.”

Concrete enforcement patterns:

• Remove local admin rights from standard users (coordinate with least privilege program).
• Block uninstall/disable actions via endpoint tool controls and OS policy.
• Restrict scripting and untrusted binaries where your enterprise standard supports it.
• Require admin elevation workflows (ticketed, time-bound) for security setting changes.

Deliverable: Evidence that non-privileged accounts cannot disable controls (see evidence section).

4) Build exception handling that is narrow, approved, and reversible

You will need exceptions (false positives, legacy apps, developer tools). SI-3(3) fails when exceptions are informal.

Minimum exception workflow:

1. Requestor submits business justification and scope (device/user/app hash/path).
2. Security reviews risk, defines compensating controls, and sets an expiration.
3. Implement exception centrally (never local user edits).
4. Monitor exception usage and alerts involving excepted items.
5. Remove or renew before expiration with re-approval.

Deliverable: Exception register + approval artifacts.

5) Monitor coverage and drift for non-privileged endpoints

Operational checks you should run continuously:

• Endpoint agent health: installed, running, and policy-compliant.
• Update posture: signatures/engines current enough for your risk tolerance.
• Tamper events: attempted disable/uninstall.
• Malware detections and containment outcomes on user endpoints.

Deliverable: Scheduled compliance reports/dashboards and alert routing to SecOps.

6) Map ownership and recurring evidence production

Assign:

• Control owner: typically Security Engineering or Endpoint Security.
• Operators: EUC/Endpoint Management, SecOps.
• GRC: evidence collection, control narrative, sampling plan.

Daydream fit: use Daydream to map SI-3(3) to a named owner, a written procedure, and a recurring evidence checklist so the control stays assessment-ready even as tooling changes.

Required evidence and artifacts to retain

Retain artifacts that prove enforcement for non-privileged users, not just tool purchase.

Recommended evidence set (keep current copies and point-in-time exports):

• Control narrative for SI-3(3): scope, intent, how enforcement works, and how exceptions are controlled. ¹
• Endpoint protection policy exports showing tamper protection, locked settings, update enforcement, and role restrictions.
• Screenshots or config records showing non-privileged users cannot disable/uninstall or alter policy.
• Agent coverage report (by device group) for in-scope endpoints and VDI pools.
• Sampled endpoint validation: proof from a standard user context (or test account) that settings are not editable and services can’t be stopped without admin elevation.
• Exception register with approvals, scope, expiration, and closure evidence.
• Monitoring/alert evidence: tamper alerts, malware detections, and incident tickets that include user endpoints.
• Change management records for policy changes impacting endpoint protection.

Common exam/audit questions and hangups

Expect these questions, and pre-build answers with artifacts:

• “Show me how a standard user could not disable endpoint protection on a corporate laptop.”
• “How do you know all non-privileged user endpoints are covered?”
• “How do you handle exceptions? Who approves them, and how do you ensure they expire?”
• “How do you detect and respond to tampering attempts?”
• “What happens if an endpoint goes out of compliance with the security policy?”

Hangups that cause findings:

• Coverage reporting includes only “checked-in” endpoints, leaving blind spots.
• Exceptions are implemented locally or by help desk without security approval.
• Policy exists, but tamper protection is off or inconsistent across device groups.

Frequent implementation mistakes (and how to avoid them)

1. Assuming SI-3(3) is satisfied by having EDR installed.
   Avoidance: prove enforcement for non-admin accounts with tamper protection and role-based restrictions.

2. Letting developers or power users keep local admin without compensating controls.
   Avoidance: define “approved admin endpoints” as a separate population with tighter monitoring, documented justification, and controlled elevation.

3. Exception sprawl.
   Avoidance: require expiration on every exception and review the exception register on a set cadence aligned to your risk appetite.

4. No evidence from the user context.
   Avoidance: keep a standard user test account and capture periodic validation steps that demonstrate “cannot disable,” “cannot uninstall,” and “policy applied.”

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for SI-3(3). Treat this requirement as assessment-driven: failure typically appears as an audit deficiency, authorization risk (ATO delays), or a control gap discovered after malware events. ¹

Risk implications if you do not operationalize SI-3(3):

• Higher likelihood that commodity malware persists due to disabled or outdated protection on user endpoints.
• Reduced confidence in incident containment because endpoints are inconsistent.
• Increased audit friction because you cannot prove technical enforcement or exception governance.

Practical 30/60/90-day execution plan

Use phased milestones without claiming specific implementation durations.

First 30 days (stabilize scope + enforce the baseline)

• Confirm in-scope endpoint populations and document exclusions.
• Export current endpoint security policies; identify where non-privileged users can alter settings.
• Turn on tamper protection and lock local UI/config where supported.
• Stand up an exception workflow and register (even if manual at first).
• Define the evidence checklist and assign owners (Daydream can hold the mapping and recurring tasks). ¹

Days 31–60 (prove operation + close drift)

• Generate coverage and health reports; reconcile against asset inventory.
• Run a small validation exercise: attempt disable/uninstall/config edits as a standard user on sampled devices; record results.
• Route tamper alerts and malware detections into your ticketing/incident process.
• Start reviewing exceptions for scope creep and missing expirations.

Days 61–90 (harden governance + make it repeatable)

• Convert the validation steps into a repeatable control test procedure for audits.
• Expand monitoring to include “agent missing,” “policy noncompliant,” and “outdated signatures/engines” alerts.
• Implement a formal change control path for endpoint security policy changes.
• Package audit-ready evidence: narrative, exports, reports, samples, and exception approvals.

Frequently Asked Questions

Does SI-3(3) require a specific endpoint protection tool (EDR vs. traditional AV)?

NIST SP 800-53 doesn’t mandate a product in the provided excerpt; it requires that malware protection meaningfully applies to non-privileged users. Pick tooling that supports central policy enforcement and tamper resistance. ¹

How do we show auditors that non-privileged users can’t disable protection?

Keep policy exports showing tamper protection and role restrictions, plus a short validation record from a standard user test proving the disable/uninstall actions fail without admin elevation. Pair that with tamper alert logs if available.

Our developers need admin rights. Does that automatically fail SI-3(3)?

No, but you must treat developer admin endpoints as an exception population with documented justification, tighter monitoring, and controlled elevation paths. Your evidence should show you made an explicit risk decision and added guardrails.

What evidence matters more: screenshots or reports?

Reports demonstrate coverage and ongoing operation; screenshots help prove configuration intent and user restrictions. Keep both, and make sure the artifacts are tied to in-scope device groups and dates.

Do SaaS-only users count as “non-privileged users” for SI-3(3)?

SI-3(3) is typically demonstrated on the systems where you can enforce malware controls, most often managed endpoints and systems in your boundary. If users access SaaS from unmanaged devices, treat that as a scope and boundary question and document your position. ²

How should we manage anti-malware exceptions for line-of-business apps?

Require central implementation, security approval, and an expiration. Keep a register with scope, rationale, compensating controls, and closure evidence so exceptions do not become permanent backdoors.

Footnotes

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

2. NIST SP 800-53 Rev. 5