PR.AA-03: Users, services, and hardware are authenticated

PR.AA-03 requires you to prove that every user, service (including APIs and service accounts), and piece of hardware that connects to your environment is authenticated before it gains access. Operationalize it by inventorying identities, enforcing strong authentication methods per identity type, and retaining reviewable evidence (configs, logs, and access reviews) that shows the controls run consistently. ¹

Key takeaways:

• Authenticate three identity classes: people, non-human services, and devices, not just employees. ¹
• Treat service-to-service auth and device enrollment as first-class controls with owners, standards, and monitoring.
• Evidence beats intent: keep configurations, logs, and periodic review records that tie back to the requirement. ²

PR.AA-03: users, services, and hardware are authenticated requirement sounds simple until you try to evidence it. Most programs have a reasonable handle on user login, then fail on two common edges: non-human identities (service accounts, workload identities, API clients) and hardware identities (endpoints, servers, network gear, IoT/OT, and “shadow” devices). PR.AA-03 expects you to authenticate all of them, consistently, before they reach systems or data. ¹

As a Compliance Officer, CCO, or GRC lead, your job is to turn that sentence into: (1) an enforceable standard, (2) a control set with clear ownership, and (3) recurring evidence that stands up in audits and customer due diligence. This page gives you a requirement-level playbook you can hand to IAM, IT, and Security Engineering with minimal translation. It focuses on decisions you must lock down (what is “authenticated” for each identity type, where it is enforced, and how you detect exceptions) and on artifacts you must retain to avoid the most common audit failure: “we do this” with no system proof. ²

Regulatory text

Requirement (excerpt): “Users, services, and hardware are authenticated.” ¹

What the operator must do: Implement technical and administrative controls that ensure:

• Human users authenticate through an approved identity provider and method before accessing corporate resources.
• Services (applications, workloads, scripts, CI/CD jobs, APIs, and service accounts) mutually authenticate using managed credentials or identity-based mechanisms.
• Hardware (endpoints, servers, network devices, and any device joining networks) is authenticated and authorized before it is trusted.

Your audit story should connect the excerpt to measurable enforcement points: SSO/MFA policies, workload identity controls, certificate/device enrollment, network access controls, and logs that prove the checks happened. ¹

Plain-English interpretation

PR.AA-03 means “no anonymous access.” Every access path needs a known, verifiable identity:

• People: “Who is this person?”
• Services: “Which workload is calling, and is it the one we expect?”
• Devices: “Is this device enrolled/attested, and is it allowed on this network?”

Authentication is distinct from authorization. Authentication confirms identity; authorization determines permissions. PR.AA-03 is the identity proof step, but your implementation will usually pair it with authorization rules to be enforceable.

Who it applies to

Entity scope: Any organization operating a cybersecurity program that uses NIST CSF 2.0 as a framework reference. ¹

Operational scope (where it shows up in practice):

• Workforce access to SaaS (email, HRIS, finance, ticketing), VPN/ZTNA, and admin consoles
• Production access (cloud consoles, Kubernetes, databases, secrets managers)
• East-west traffic (service-to-service in VPC/VNET, cluster, service mesh)
• Corporate networks (wired/wireless), guest networks, and remote access
• Device onboarding (MDM/UEM, certificates, EDR enrollment)
• Third-party connections (support portals, SFTP, B2B APIs), where non-human identities are common

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

Step 1: Set an authentication standard by identity type

Create a one-page “Authentication Standard” that answers these questions:

Identity type	Required auth method	Where enforced	Exceptions allowed?	Control owner
Human users	SSO + MFA for privileged and remote access	IdP, VPN/ZTNA, app settings	Documented break-glass only	IAM lead
Service identities	Managed workload identity or short-lived tokens; no shared passwords	Cloud IAM, service mesh, API gateway	Temporary with expiry	Platform/SRE
Hardware/devices	Device enrollment + cert-based auth or equivalent	MDM/UEM, NAC/Wi-Fi, VPN posture	Isolated networks only	IT Ops/NetOps

Keep it readable. Auditors and customers will ask for a standard before they ask for logs.

Step 2: Build (or validate) inventories for users, services, and hardware

You cannot authenticate what you have not identified.

Minimum inventory expectations:

• Users: authoritative source (HRIS), IdP directory groups, privileged accounts list
• Services: service accounts in cloud IAM, API clients, CI/CD tokens, Kubernetes service accounts, secrets manager entries
• Hardware: MDM device list, EDR fleet, DHCP/NAC logs, cloud instance inventory, network equipment inventory

Operator tip: make “unknown identity discovered” a ticketable event. If your discovery is informal, the gap will persist.

Step 3: Centralize authentication for human access

Implement or confirm:

• SSO for SaaS and internal apps through the IdP
• MFA policies, with stricter rules for admin access paths
• Administrative access separation (separate admin roles, break-glass accounts with compensating controls)
• Conditional access where available (device posture, location, risk signals)

Evidence you want: screenshots/exports of IdP policies, app SSO settings, and a sample authentication log showing successful MFA events.

Step 4: Lock down service authentication (the most common gap)

Service-to-service authentication fails quietly because “it works” until compromise.

Implement:

• No shared credentials: prohibit shared “integration” usernames/passwords for automated jobs
• Prefer identity-native methods: cloud workload identity (AWS IAM roles, Azure managed identities, GCP service accounts) or service mesh mTLS where applicable
• Token hygiene: rotate credentials, prefer short-lived tokens, restrict scopes, bind tokens to workloads where possible
• Secrets management: store secrets in a managed secrets vault, not in code repos or CI variables without governance
• API authentication: require signed tokens/keys; avoid unauthenticated endpoints except explicitly approved public services

Evidence you want: a register of service accounts, their owners, rotation/expiry settings, and sample logs from the API gateway/service mesh showing authenticated calls.

Step 5: Authenticate hardware before trust (device identity + network admission)

Pick enforcement points that match your environment:

• Endpoints: MDM enrollment required to access corporate resources; certificates for Wi-Fi/VPN where feasible
• Network access control (NAC) or equivalent: only known devices can join internal networks; unknown devices go to quarantine/guest
• Server/workload identity: server certificates, instance identity documents, or cloud-native instance identities
• IoT/OT: isolate by network segment; require device identity or gateway authentication before access to business systems

Evidence you want: MDM compliance policies, NAC rules, Wi-Fi EAP-TLS settings (or equivalent), and reports showing enrolled devices vs. noncompliant devices.

Step 6: Monitor and review exceptions

Define “authentication failure” events and respond:

• Repeated failed logins (users)
• New service account created without an owner tag
• API calls missing auth headers
• New MAC addresses appearing on internal VLANs
• Device removed from MDM but still accessing VPN

Run recurring reviews:

• Privileged access review (users)
• Service account review (non-human identities)
• Device fleet review (hardware)

Daydream fit: map PR.AA-03 to a control owner, required evidence list, and a recurring collection schedule so you can produce consistent audit packets without rebuilding them each cycle. ²

Required evidence and artifacts to retain

Keep evidence in an “authentication controls” folder with a simple index. Recommended artifacts:

• Policies/standards
  • Authentication Standard (covers users, services, hardware)
  • Access control policy and exception process
• System configurations (exported or screenshot)
  • IdP SSO/MFA policies and conditional access rules
  • Service mesh/API gateway auth configuration (where applicable)
  • Secrets manager policies and rotation settings (representative samples)
  • MDM/UEM enrollment and compliance policies
  • NAC/Wi-Fi/VPN access policies tied to device identity/posture
• Operational records
  • Inventories: users, service accounts, device fleet
  • Access review tickets/approvals (privileged, service accounts)
  • Exceptions register with expiry and compensating controls
• Logs and reports
  • Authentication logs (IdP), admin console sign-ins
  • API gateway/service auth logs (sample queries and outputs)
  • MDM compliance reports and device enrollment exports

Common exam/audit questions and hangups

Expect these questions and prepare “show me” evidence:

• “Do you enforce MFA for administrative access? Show the policy and an authentication log sample.”
• “How do you authenticate service-to-service traffic? Where are service credentials stored and rotated?”
• “List all service accounts and prove each has an owner and a business purpose.”
• “How do you stop unknown devices from joining internal networks?”
• “What is your break-glass process, and how do you monitor its use?”

Hangup patterns:

• “We use MFA” without scoping it to admin paths, remote access, and high-risk apps.
• Service accounts treated as invisible plumbing with no ownership.
• Device lists spread across tools with no single “authoritative” view.

Frequent implementation mistakes and how to avoid them

1. Mistake: Only covering human users.
   Fix: create separate control statements and evidence sets for users, services, and hardware. PR.AA-03 names all three. ¹

2. Mistake: Shared integration accounts.
   Fix: require per-system service identities, ownership tags, and credential rotation or identity-native auth.

3. Mistake: “Authenticated” but not enforced everywhere.
   Fix: identify all ingress points (VPN, admin consoles, APIs, internal networks). Tie each to an enforcement control.

4. Mistake: No exception expiry.
   Fix: require exceptions to have an end date, compensating controls, and a reviewer.

5. Mistake: Evidence is ad hoc screenshots.
   Fix: schedule recurring exports, store them with timestamps, and keep a short evidence index keyed to PR.AA-03. ²

Risk implications (why auditors care)

Authentication gaps convert small mistakes into large incidents:

• A stolen password becomes a breach if MFA is missing on remote/admin access.
• A hard-coded API key becomes broad compromise if service identity is shared and unscoped.
• An unmanaged device becomes a foothold if it can join internal networks without device identity checks.

From a governance perspective, PR.AA-03 is also an evidence test. A program can have strong technical controls and still fail a review if it cannot prove consistent operation. ²

Practical execution plan (30/60/90-day)

You asked for speed. Use these phases as a delivery plan; adjust to your environment and risk tolerance.

First 30 days (stabilize + map)

• Assign a control owner for users, services, and hardware authentication.
• Publish the one-page Authentication Standard and exception workflow.
• Identify your enforcement points: IdP, VPN/ZTNA, API gateway/service mesh, MDM, NAC/Wi-Fi.
• Build baseline inventories (even if imperfect) and define what “unknown” means.

Days 31–60 (enforce + remove high-risk gaps)

• Expand SSO coverage and block direct logins where possible.
• Enforce MFA on admin access paths and remote access.
• Catalog service accounts and require ownership tags; eliminate shared credentials in critical integrations.
• Require device enrollment for corporate endpoints; quarantine unknown devices where feasible.

Days 61–90 (operationalize + evidence)

• Start recurring access reviews (privileged users and service accounts) and retain approvals.
• Implement monitoring for new service identities and unknown devices.
• Produce an audit-ready PR.AA-03 evidence packet: standard, configs, inventories, review records, and sample logs.
• In Daydream, map PR.AA-03 to the policy, procedure, control owner, and recurring evidence collection schedule so evidence stays current without heroic effort. ²

Frequently Asked Questions

Does PR.AA-03 require MFA everywhere?

PR.AA-03 requires authentication for users, services, and hardware, but it does not prescribe a specific method in the excerpt. Set an internal standard that defines where MFA is mandatory (for example, admin and remote access) and retain evidence that enforcement matches the standard. ¹

What counts as “services” for this requirement?

Treat non-human identities broadly: service accounts, API clients, workloads, automation scripts, CI/CD jobs, and integrations run by third parties. If it can access your systems without a person typing a password, it should have an authenticated service identity with an owner.

How do I evidence service-to-service authentication without overwhelming auditors with logs?

Provide configuration evidence (API gateway/service mesh settings) plus a small set of representative log extracts that show authenticated requests. Pair that with a service account inventory showing owners and credential management.

Do hardware devices need certificates to satisfy PR.AA-03?

The excerpt does not mandate certificates. Certificates are a common method; the key is that devices are authenticated through a repeatable enrollment and admission control process you can prove with configurations and device inventory exports. ¹

What about “break-glass” accounts that bypass normal authentication controls?

Allow them only through a documented exception with compensating controls, tight access restrictions, and monitoring. Retain evidence of approvals and logs of each use.

How should I handle third-party access under PR.AA-03?

Require third parties to authenticate through your approved methods (federation/SSO where possible, otherwise controlled accounts with MFA) and avoid shared accounts. Treat third-party integrations as service identities with owners and credential controls.

Footnotes

1. NIST CSWP 29

2. NIST CSF 1.1 to 2.0 Core Transition Changes