They should govern them as separate trust subjects even when they use the same platform. Vendors need tight onboarding, expiry, and offboarding controls, while machine identities need inventory, scope review, and recovery handling that matches their operational role. Treating all non-human access the same leaves gaps in ownership and revocation.
Why shared access surfaces need separate trust models
When vendors and machine identities land on the same platform, the platform is not the trust boundary. The trust boundary is the subject behind the access. Vendors are external parties with contractual terms, renewal dates, and removal obligations; machine identities are operational actors with system-owned scope, dependency chains, and recovery needs. Mixing those models usually creates blind spots in ownership, expiry, and revocation.
A practical separation also prevents teams from applying the wrong lifecycle rule to the wrong subject. A vendor account should be validated as a third-party relationship, while a machine identity should be validated as a workload, service, or integration dependency. Shared tooling can still work, but the control model has to reflect who or what is using the access.
That distinction matters most where the same console, vault, or identity provider is used for both. Shared infrastructure can make governance simpler to administer, but it does not make the underlying trust subjects interchangeable. The right question is not whether they authenticate through the same platform, but whether they are governed with different ownership, review, and termination paths.
What changes for vendors versus machine identities
Vendor access should be treated as time-bound external access. That means strong onboarding checks, narrowly scoped entitlements, defined expiry, and explicit offboarding when the commercial or operational relationship ends. The main control objective is to prevent lingering external access after the business need has passed.
Machine identities need a different operating model because they are embedded in system behaviour rather than a person’s engagement. Their access should be inventoried, scoped to the minimum functional requirement, and reviewed against the service’s actual runtime role. If a machine identity supports a production workflow, recovery handling and dependency mapping matter as much as the initial grant.
Because machine identities often automate actions, they also need attention to renewal, rotation, and failure handling. If a secret expires or a certificate is revoked without understanding downstream dependencies, the failure can become an availability issue. If a vendor credential is left active, the failure becomes an unnecessary exposure problem. Same platform, different lifecycle risk.
How to govern the shared surface without collapsing the subjects
Start by separating policy and inventory, even if the authentication stack is unified. Maintain a vendor register with business owner, contract owner, expiry date, and offboarding trigger. Maintain a machine identity register with system owner, workload purpose, dependency map, and recovery contact. If one record tries to carry both models, accountability usually degrades.
Where the access surface is shared, use controls that preserve subject identity in the audit trail. Access reviews should ask whether a grant belongs to a third party or to an operational workload, because the review criteria differ. Vendor access is judged by continuing business need and contractual validity; machine identity access is judged by operational necessity and blast radius.
When teams need a broader reference point for this separation, the comparison between Human vs Non-Human Identity is useful, and the Service Account Security Guide gives a practical lens for the machine side of the model. For the trust boundary itself, SPIFFE’s workload identity model is a good external anchor: SPIFFE workload identity specification.
Risk and Threat Considerations
When vendors and machine identities are governed as one bucket, revocation and review gaps are the usual failure mode. An external vendor can retain access longer than intended, while a machine identity can be over-scoped because it was provisioned for operational convenience rather than least privilege. Both conditions increase the chance of unauthorized use or lateral movement.
Failure mechanism: Shared governance hides different termination triggers, so one subject is removed on contract end while the other remains active because no one mapped it to a service dependency, or vice versa.
Impact: Stale external access raises third-party exposure, and mismanaged machine access can interrupt production or expand the blast radius of a compromise.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5, CSA Cloud Controls Matrix and CIS Controls v8 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Shared access surfaces need distinct lifecycle control for vendor and machine credentials. |
| AC-2 — Account Management | The question is about governing who may keep access and when it must end. | |
| AC-6 — Least Privilege | Separate trust subjects should not inherit the same permissions just because they share a platform. | |
| Recommendation — Enforce distinct issuance, rotation, and revocation rules for each trust subject. Track each vendor and machine account separately and disable it at the right lifecycle point. Limit each vendor or machine identity to the minimum access needed for its role. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access control | The topic is fundamentally about governing different access subjects on the same surface. |
| Recommendation — Separate access rules for external parties and operational identities. | ||
| CSA Cloud Controls Matrix | IAM — Identity and Access Management | Shared vendor and machine access should be governed through distinct identity lifecycle and entitlement controls. |
| Recommendation — Apply separate identity lifecycle and entitlement rules to vendors and machine identities. | ||
| CIS Controls v8 | CIS-5 — Account Management | Account lifecycle and separation are central when multiple trust subjects share one access surface. |
| Recommendation — Inventory, review, and remove vendor and machine accounts independently. | ||
Practitioner Guidance
What to verify: Confirm that every shared platform account is tagged to exactly one trust subject at the governance layer, even if the platform uses a common authentication method. If the same account can be justified both as a vendor account and as a workload account, the record is too ambiguous to govern safely.
Decision rule: If the access supports a contracted relationship, treat it as vendor access with expiry and offboarding controls. If the access supports system behaviour, treat it as machine identity access with inventory, scope, and recovery controls. Do not let platform convenience override lifecycle design.
Practitioner takeaway: The key control is not separate technology, but separate accountability, because revocation, review, and failure handling only work when each trust subject has its own lifecycle.
Related resources from NHI Mgmt Group
- Why do access review programmes struggle when human and machine identities share the same control plane?
- Should organisations manage human and machine identities under the same access governance model?
- How should security teams run access reviews for non-human identities?
- How should security teams govern non-human identities that have persistent access?