Security teams should govern machine identities the same way they govern privileged access: assign an owner, define a specific purpose, limit scope, and review it continuously. In practice, that means tracking service accounts, certificates, APIs, and connectors as non-human identities with their own lifecycle, not as background infrastructure. A machine identity should never have broader access than its workflow requires.
Why This Matters for Security Teams
Industrial environments compress business continuity, safety, and cybersecurity into the same control plane. Machine identities often sit inside OT links, plant connectors, historian integrations, service accounts, and API-enabled maintenance tools, so a weak identity becomes an operational risk, not just an IT issue. NHI governance should therefore treat every service principal, certificate, token, and connector as a bounded identity with an owner, purpose, and review cycle. That is consistent with NIST Cybersecurity Framework 2.0 and the NHI lifecycle guidance in Ultimate Guide to NHIs — Lifecycle Processes for Managing NHIs.
The practical mistake is assuming “machine” means “safe to leave alone.” In reality, industrial credentials often persist across engineering workstations, vendor remote access, and integration layers that were never built for modern identity controls. The result is standing privilege, weak offboarding, and excessive trust between systems that were only meant to exchange data, not inherit each other’s authority. In practice, many security teams encounter identity sprawl only after a maintenance account, API key, or certificate has already been reused outside its original production workflow.
How It Works in Practice
Good governance starts by inventorying every machine identity and attaching three basics to it: ownership, business purpose, and expiry. For industrial settings, that includes PLC-connected service accounts, SCADA integrations, remote support tokens, certificates on edge devices, and API credentials used by data pipelines. The control objective is not merely to track them, but to make them measurable and enforceable across issuance, rotation, and revocation. That aligns with the identity assurance principles in NIST SP 800-63 Digital Identity Guidelines and the lifecycle, visibility, and offboarding emphasis in Top 10 NHI Issues.
- Assign each identity to a named system owner, not a shared operations group.
- Scope access to one workflow, one plant segment, or one integration path where possible.
- Use JIT issuance for credentials that do not need to exist continuously, and revoke them when the task ends.
- Prefer short-lived tokens and certificates over static secrets embedded in code, scripts, or vendor tools.
- Log issuance, use, and revocation events so reviews can focus on actual usage, not assumptions.
Where vendors or integrators must connect into industrial systems, current guidance suggests treating that access as a separate NHI boundary with its own monitoring and offboarding rules. The same is true for certificates used by machine-to-machine channels: if the credential outlives the workflow, it becomes a standing access path. These controls tend to break down when legacy OT equipment cannot support rotation, short token lifetimes, or detailed logging because the identity layer was never designed for frequent change.
Common Variations and Edge Cases
Tighter machine-identity controls often increase operational overhead, requiring organisations to balance uptime against credential turnover, vendor support, and maintenance windows. That tradeoff is real in industrial environments, especially where asset lifecycles are long and patch windows are rare. Best practice is evolving, but the general direction is clear: reduce standing privilege first, then modernise the most exposed identities with stronger rotation and monitoring. The lifecycle and audit recommendations in Ultimate Guide to NHIs — Regulatory and Audit Perspectives help structure that work.
One common edge case is a legacy plant where a certificate or service account cannot be replaced without operational disruption. In those cases, teams should isolate the identity, restrict network reach, and add compensating monitoring until the system can be remediated. Another edge case is third-party remote maintenance, where the safest pattern is often time-bound access with explicit approval rather than persistent credentials. Industrial teams should also review incident lessons such as the JetBrains GitHub plugin token exposure and the Schneider Electric credentials breach, both of which show how quickly machine credentials can become enterprise-wide risk once they leak. For organisations formalising the programme, the key is to map identity controls to plant-critical processes before automation expands the blast radius.
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 | Covers rotation and lifecycle control for machine credentials in industrial settings. |
| NIST CSF 2.0 | PR.AC-4 | Least-privilege access control is central to governing machine identities safely. |
| NIST Zero Trust (SP 800-207) | Policy enforcement and continuous verification | Industrial machine identities need continuous verification, not implicit trust. |
Enforce request-time verification and segmentation for every machine-to-machine access path.
