Both, but service accounts often deserve earlier attention because they are frequently forgotten, broadly scoped, and poorly owned. Human reviews alone leave a large amount of standing non-human privilege untouched. A complete programme has to cover the whole identity graph, not one identity type at a time.
Why this review should not start with humans only
Human accounts are usually the most visible part of a privileged access programme, but they are not the whole risk surface. Service accounts, application identities, shared integrations, and automation principals often accumulate standing privilege quietly, especially where ownership is vague or reviews are calendar-driven rather than evidence-driven. If privileged access reviews only start with people, a large class of persistent access can remain untouched.
That is why the review order should follow exposure and blast radius, not organisational comfort. A service account that can reach production data, reset credentials, or call privileged APIs may be more operationally important than a human admin account that is already tightly monitored. The strongest reviews begin where access is broadest, least explained, or hardest to trace back to a current business need. For a deeper treatment of how non-human identities fit into the wider control model, see Ultimate Guide to NHIs.
In practice, “human first” is often a reporting convenience, not a control strategy. It can reduce review volume quickly, but it does not necessarily reduce risk quickly. Reviews should be designed around privilege concentration, privilege persistence, and reviewability, because those are the conditions that determine whether access is actually safe to keep.
Why service accounts often deserve earlier attention
Service accounts often deserve earlier attention because they are frequently over-scoped, poorly documented, and difficult to assign to a single accountable owner. They are also common places for long-lived secrets, inherited permissions, and cross-environment access paths to accumulate. In other words, they are not just another account type, they are often the place where governance breaks down first.
That matters because non-human privilege can become operationally invisible. A human reviewer may know who the account belongs to, but still not know why it exists, whether it is still needed, or whether its permissions reflect the current system design. When service accounts are included early, reviews can catch standing access that human-only campaigns never surface, especially in infrastructure, integrations, and automated workflows.
When the review scope includes machine and application identities, service account security becomes a practical ownership and entitlement problem, not just an authentication problem. The review should answer three basic questions: who owns it, what does it reach, and what breaks if it is reduced or removed.
How to sequence privileged access reviews without missing the real risk
A practical sequence is to review the accounts with the highest blast radius first, then move outward to lower-impact populations. Start with accounts that can affect production systems, credentials, security tooling, or sensitive business workflows, because those are the ones most likely to create disproportionate harm if misused. Then move to the broader population of humans, contractors, service accounts, and shared or orphaned identities.
Privileged access reviews are also more effective when they are identity-graph aware. That means tracing inherited permissions, linked secrets, and downstream dependencies before deciding whether access is valid. A review that only checks a named account can miss the real access path if the privilege is being exercised through a token, vault entry, role chain, or service principal. The review should therefore validate both the account and the mechanism that gives it power.
One useful pattern is to review standing access with a bias toward exception handling. If an account cannot be clearly explained, cannot be tied to an owner, or has not been used within a justified window, it should move to remediation rather than remain in the queue for a later campaign. For teams building a repeatable programme, the access reviews and certification guide is the best next step for designing a review that actually removes access instead of rubber-stamping it.
Risk and Threat Considerations
Privileged access reviews fail when organisations assume the main risk sits with named people only. Service accounts, tokens, and other non-human identities can retain powerful access long after staff changes, application changes, or ownership drift have made that access hard to justify. That creates a standing exposure that is attractive to attackers and easy to overlook in manual review cycles.
Failure mechanism: Service accounts are often reused, unrotated, or insufficiently owned, which lets dormant but privileged access survive beyond the business need that created it. Once compromised, that access can be used for lateral movement, data access, or administrative actions without triggering the same review friction as a human account.
Impact: The result is persistent privileged exposure, slower detection of abuse, and a higher chance that a single overlooked account can undermine an otherwise well-run review programme. If the service account can reach critical systems, the security impact is often larger than the review effort saved by focusing on humans first.
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 and CSA Cloud Controls Matrix set the technical controls, and ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Service account reviews hinge on secret lifecycle and credential control. |
| AC-6 — Least Privilege | Privileged access reviews exist to reduce excessive account permissions. | |
| AU-6 — Audit Record Review, Analysis, and Reporting | Review programmes need evidence to verify privileged use and ownership. | |
| Recommendation — Review and rotate service account credentials on a defined lifecycle. Remove unnecessary privileges and revalidate least privilege for privileged accounts. Use audit evidence to confirm account activity and justify continued access. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access control | The question is about which privileged identities should be reviewed first. |
| A.5.18 — Access rights | Access-rights review and removal are central to privileged access certification. | |
| Recommendation — Apply access control reviews to privileged accounts based on business need. Recertify access rights and remove unjustified privileged entitlements. | ||
| CSA Cloud Controls Matrix | IAM — Identity and Access Management | Cloud and service accounts require identity governance across humans and machines. |
| Recommendation — Include human and non-human identities in IAM review cycles. | ||
| OWASP Non-Human Identity Top 10 | NHI-01 — Improper Offboarding | Service accounts often persist after systems, owners, or uses change. |
| NHI-05 — Overprivileged NHI | The question asks which accounts should be prioritised when privilege is excessive. | |
| Recommendation — Retire stale non-human identities when ownership or use has ended. Prioritise accounts with the broadest non-human privilege for review and reduction. | ||
Practitioner Guidance
What to prioritise: Start with privileged identities that combine high reach, weak ownership, and standing access. If an account can affect production, security controls, or sensitive data, it belongs near the front of the queue regardless of whether it is human or non-human.
What to verify: For each privileged account, verify a named owner, a current business purpose, the actual systems it can reach, and whether that access is still required. If any of those four cannot be demonstrated, treat the account as a remediation candidate, not a review pass.
Practitioner takeaway: Prioritise by blast radius and governance quality, not by identity type alone, because the most dangerous privilege is usually the one that is standing, poorly owned, and hardest to explain.
Related resources from NHI Mgmt Group
- Should organisations treat service accounts like human users in access reviews?
- How should security teams run access reviews for non-human identities?
- Should organisations prioritise external exposure or internal credential governance first?
- Should organisations prioritise passwordless or privileged access modernisation first?