An approval hierarchy is the ordered set of roles that can review or authorise an access request. It reduces ambiguity only when each level has clear authority, defined boundaries, and accountability for the entitlement being approved.
Expanded Definition
An approval hierarchy is the decision chain that determines who can review, escalate, or authorise an access request for a non-human identity. In NHI governance, it is not enough to name approvers; each step must map to a specific entitlement scope, risk threshold, and accountability boundary.
Definitions vary across vendors when approval flows are embedded in PAM, IAM, ticketing, or workflow automation platforms, so the practical meaning depends on who can approve what, under which conditions, and with what evidence. A sound hierarchy separates routine requests from high-risk exceptions, and it should align with least privilege, segregation of duties, and traceable audit records. That aligns closely with the control intent of the NIST Cybersecurity Framework 2.0, especially where access decisions must be governed, repeatable, and reviewable.
When approval tiers are vague, the result is often rubber-stamping or approval sprawl, where multiple roles can approve the same entitlement without clear ownership. The most common misapplication is treating an approval hierarchy as a staffing chart, which occurs when org structure is copied into access workflows without entitlement-specific authority.
Examples and Use Cases
Implementing approval hierarchy rigorously often introduces review latency, requiring organisations to weigh stronger control against slower access delivery for time-sensitive operations.
- A developer requests production API-key access, and a team lead approves the request while a security approver is required for elevated scopes or exceptions.
- A service account needs a new certificate for an integration, and the request must pass through application ownership, platform operations, and security review before issuance.
- A temporary third-party connection is requested, and the hierarchy requires business sponsor approval plus a control owner sign-off before credentials are granted.
- An emergency privilege request is escalated through a separate path, with stricter evidence and post-approval validation to ensure the entitlement matches the incident scope.
- Workflow design is informed by NHI risk patterns documented in the Ultimate Guide to NHIs, especially where approval controls must compensate for excessive privileges and poor visibility.
In practice, approval hierarchies are most useful when the approver is also accountable for the business use of the entitlement, while the control owner validates technical fit. The NIST Cybersecurity Framework 2.0 supports this separation by emphasising governed access decisions and ongoing accountability.
Why It Matters in NHI Security
Approval hierarchy matters because NHIs are high-scale, high-privilege, and often poorly observed. NHIMG reports that Ultimate Guide to NHIs found 97% of NHIs carry excessive privileges, which means an approval mistake can grant broad, lasting access rather than a narrow, reversible permission. Without a disciplined hierarchy, approvals become an attack path for privilege creep, insider misuse, and accidental overexposure.
For governance, the key risk is not only who approves, but whether the approver understands the entitlement’s blast radius and expiry conditions. That is why approval hierarchy should connect to access reviews, revocation, and exception handling, not sit apart as a one-time checkpoint. Where the hierarchy is weak, organisations often discover that a service account or API key was approved without clear ownership, making incident response slower and remediation harder.
Organisations typically encounter the cost of a weak approval hierarchy only after a compromised secret, unauthorised integration, or audit failure, at which point entitlement approval becomes operationally unavoidable to address.
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 address the attack and risk surface, while NIST CSF 2.0 and NIST Zero Trust (SP 800-207) set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-03 | Approval paths should prevent excessive NHI permissions and unclear authorisation. |
| NIST CSF 2.0 | PR.AA-01 | Access decisions must be governed, traceable, and consistent with identity assurance. |
| NIST Zero Trust (SP 800-207) | Zero Trust limits implicit trust and supports per-request access decisions. |
Require entitlement-specific approvals and separate technical validation from business authorisation.
