They often design SoD around named employees and forget that non-human accounts can carry the most sensitive privileges. Service accounts, shared accounts, and orphaned accounts need ownership, conditions, and review logic of their own. If they are excluded, SoD coverage stops where machine access begins.
Why This Matters for Security Teams
Segregation of duties is often built as if every privilege belongs to a named employee with a manager, HR record, and a predictable approval chain. That model breaks down for service account and shared accounts, where the real risk is not intent but hidden reach: unattended credentials, broad reuse, and privileges that outlive the workflow they were created for. NHI Management Group’s Ultimate Guide to NHIs shows that only 5.7% of organisations have full visibility into their service accounts, which means SoD reviews can be structurally incomplete before they start.
This matters because machine accounts are often the most powerful identities in the environment, yet they are reviewed least often. When shared accounts are excluded from SoD logic, approvers may still sign off on transactions, deployments, or data changes without seeing the account that actually performed them. The result is a governance gap where accountability is asserted in process documents but absent in technical controls. The NIST Cybersecurity Framework 2.0 reinforces the need for identity governance that is measurable, continuous, and tied to risk, not just to employee records. In practice, many security teams discover SoD failures only after a credential is reused, not through a planned control test.
How It Works in Practice
Effective SoD for non-human identities starts by treating each service account, shared account, API key, and workload identity as a governed asset with its own owner, purpose, and lifecycle. The control question is not only “who can log in?” but also “what can this identity do, under what conditions, and who is accountable when it is used?” That is why NHI programs typically pair SoD with ownership metadata, scoped entitlements, and review rules that are distinct from employee access reviews. NHI Management Group’s 52 NHI Breaches Analysis repeatedly shows that overprivileged machine identities become breach accelerators when they are left outside standard governance loops.
- Assign a business and technical owner to every non-human account, including break-glass and shared automation accounts.
- Map each account to a documented purpose, system dependency, and allowable use case.
- Review SoD on the action level, not just the account level, so conflicting functions are separated in the workflow that the account actually supports.
- Use time-bound approvals and periodic recertification for accounts that cannot be uniquely attributed to a single person.
- Prefer workload identity and short-lived credentials where possible, because static shared secrets make SoD monitoring much harder.
For workloads that behave like autonomous agents or highly dynamic automation, current guidance suggests moving from static role assignment toward runtime policy checks and just-in-time access. The NIST Privacy Framework is not a direct SoD standard, but its emphasis on context, data use, and accountable decision-making aligns with the broader governance shift. These controls tend to break down when shared accounts are embedded in legacy batch jobs or vendor-managed integrations because the true actor cannot be cleanly attributed at review time.
Common Variations and Edge Cases
Tighter SoD for shared and service accounts often increases operational overhead, requiring organisations to balance stronger accountability against release speed and platform complexity. That tradeoff is especially visible in environments with legacy applications, managed service providers, or CI/CD pipelines that still depend on shared credentials. In those cases, best practice is evolving rather than settled: some teams accept limited shared access but compensate with enhanced logging, network restrictions, and stronger approval workflows, while others push for full replacement with per-workload identities.
One common mistake is assuming every shared account can be treated like a normal user account with a manager attestation. That is rarely true. Orphaned accounts, emergency accounts, and machine-to-machine integrations need separate review logic because their risk is defined by function and privilege, not by org chart membership. Another gap appears when organizations review password rotation but ignore whether the account still violates SoD by design.
Where shared access is unavoidable, the safest pattern is narrow scope, short duration, and explicit exception handling with expiration dates. For broader NHI governance context, the Ultimate Guide to NHIs is useful for framing lifecycle control, while the 2024 Non-Human Identity Security Report shows the maturity gap that makes these exceptions risky in the first place. Organisations that delay this shift often find that SoD exceptions become permanent because no one can safely unwind the dependency.
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 and CSA MAESTRO address the attack and risk surface, while NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 | SoD gaps often stem from unmanaged non-human ownership and lifecycle. |
| NIST CSF 2.0 | PR.AC-4 | Least-privilege access reviews are central to SoD enforcement for machine identities. |
| CSA MAESTRO | MAESTRO addresses governance for autonomous and machine-driven access paths. |
Apply runtime policy, ownership, and lifecycle controls to non-human accounts used in automation.
