Human access reviews are usually role- and employment-driven, with clear ownership and recertification points. Machine identity reviews must focus on system dependency, credential lifecycle and operational necessity, because a service account can outlive a team, an application or even a platform migration. That makes retirement and rotation as important as approval.
Why human access reviews and machine identity reviews are not the same control
Human reviews are primarily about whether a person should still have access based on job role, employment status, and segregation of duties. machine identity reviews ask a different question: whether a service account, workload, API client, or certificate still has a valid operational purpose, the right scope, and a defensible credential lifecycle. The ownership model, evidence, and remediation path are therefore different.
The review lens also changes the unit of accountability. A human account can usually be tied to a manager, HR event, or team owner. A machine identity may be shared across systems, inherited from a deployment pipeline, or required by a business process that no single team fully understands. That means the reviewer has to verify dependency, not just named ownership.
For machine identities, the useful evidence is often technical rather than organisational: service mapping, token or certificate expiry, last use, rotation status, and whether the identity can be replaced by a narrower mechanism. For human access, the evidence is more likely to be role fit, entitlement necessity, and whether the access still matches the person’s current duties.
What changes in the review criteria, approval logic, and removal decision
Human access reviews are usually periodic recertifications, and the expected outcome is approval, reduction, or removal based on business need. Machine identity reviews should be lifecycle reviews as much as entitlement reviews. They need to answer whether the identity is still needed, whether its secret material is still valid, and whether its permissions are broader than the workload actually requires.
This is why retirement matters more for machine identities than it does for most human accounts. A stale service account can survive a team change, a refactor, a migration, or an application decommissioning if nobody is watching the dependency chain. In practice, that makes service account security as much about decommissioning and scope reduction as it is about approval.
Rotation also plays a larger role. If the identity depends on long-lived secrets, the review has to test whether those credentials can be rotated without breaking production and whether the application can use a stronger pattern. Where certificate-based identity is involved, the lifecycle is often governed by expiry and renewal mechanics rather than a simple access recertification cycle, which is why machine identity certificate lifecycle management deserves separate treatment.
For people, revocation usually means disabling access. For machines, revocation may mean rotating a secret, reissuing a certificate, updating a deployment reference, or removing an unused integration. That difference matters because a technically “approved” machine identity can still be unsafe if the credential cannot be retired cleanly.
How to run both review types without mixing the failure modes
Use different reviewer questions for the two populations. Human access review questions should focus on role fit, privilege creep, and whether access still matches job function. Machine identity review questions should focus on dependency, last known use, secret age, blast radius, and whether the identity is production-critical, replaceable, or orphaned.
Where the two populations intersect, treat the overlap carefully. If a person can approve or operate a machine identity, you need to know whether that is part of normal administration or a sign of shared accountability that hides risk. Human vs Non-Human Identity is useful here because it separates the ownership and governance questions that often get blurred in mixed environments.
The practical operating model is to tie human reviews to employment and role changes, while tying machine reviews to inventory, dependency mapping, rotation cadence, and retirement triggers. If the machine identity cannot be mapped to a live service, or if no one can explain why it still exists, that is usually a removal candidate rather than a recertification candidate. NHI lifecycle management is the right lens for that decision.
For teams that want a broader operating pattern, access reviews and certification should be extended so that machine identities are not just approved or denied, but actively measured for ongoing necessity, ownership clarity, and closure of unused access.
Risk and Threat Considerations
Machine identity reviews carry higher residual risk when organisations treat them like employee recertification. The danger is not only excess privilege, but also hidden persistence: stale secrets, orphaned service accounts, and certificates that continue to authenticate long after the business owner has lost sight of them. That creates a quiet but durable attack path.
Failure mechanism: A machine identity outlives the system or team that created it, then remains valid because no one tracks dependency, expiry, or rotation failure across the full lifecycle.
Impact: An attacker, former vendor, or unintended internal user can retain or regain access through a credential that should already have been retired, increasing lateral movement and unauthorized access risk.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 addresses the attack surface, NIST SP 800-53 Rev 5 sets the technical controls, and ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 — Improper Offboarding | Machine identities can outlive systems and teams, making retirement central to reviews. |
| NHI-07 — Long-Lived Secrets | Machine identity reviews must assess secret age and rotation, not just approval status. | |
| NHI-05 — Overprivileged NHI | Machine review logic must test whether permissions exceed the workload's real need. | |
| Recommendation — Check that every machine identity has a defined retirement trigger and revoke it when the workload ends. Inventory long-lived secrets and force rotation where credential age exceeds policy. Reduce machine identity permissions to the minimum scope required by the dependent service. | ||
| NIST SP 800-53 Rev 5 | AC-2 — Account Management | Both people and machine accounts need lifecycle tracking, review, and timely removal. |
| IA-5 — Authenticator Management | Machine identity reviews hinge on secret, token, and certificate lifecycle management. | |
| IA-9 — Service Identification and Authentication | Machine identities authenticate as services, workloads, or APIs, so their review differs from human access. | |
| Recommendation — Review and disable dormant or unnecessary accounts on a defined cadence. Rotate, protect, and expire authenticators according to their lifecycle requirements. Validate service-to-service authenticators and remove those no longer needed. | ||
| ISO/IEC 27001:2022 | A.5.18 — Access rights | Access rights reviews and revocation are central to distinguishing human and machine governance. |
| A.8.2 — Privileged access rights | Machine identities often carry elevated access and need separate privileged review logic. | |
| Recommendation — Recertify access rights on a defined schedule and revoke unnecessary access promptly. Apply tighter approval and periodic review to privileged accounts and service identities. | ||
Practitioner Guidance
What to verify: For human access, verify the reviewer can confirm role fit and current need. For machine identities, verify the service owner, the downstream dependency, the secret or certificate expiry path, and the rollback plan if rotation breaks an application.
Decision rule: If the identity is tied to a live workload, approval alone is not enough. Require evidence that the credential can be rotated or retired safely, and treat any identity with no clear owner or no known dependency as a removal candidate rather than a standing exception.
Common mistake: Teams often use the same review form for both populations. That usually produces good employee recertification outcomes but weak machine identity hygiene, because it misses orphaning, long-lived secrets, and hidden production dependencies.
Practitioner takeaway: Human reviews ask whether access still matches the person; machine reviews ask whether the identity still deserves to exist at all, and whether it can be rotated or removed without breaking the system.
Related resources from NHI Mgmt Group
- What is the difference between human identity reviews and NHI access reviews?
- What is the difference between managing human IAM and non-human identity access in cloud environments?
- What is the difference between managing human access and managing agent access?
- What is the difference between human access reviews and agent access reviews?