They should treat service accounts, tokens, certificates, and API keys as governed identities with ownership, expiry, rotation, and revocation rules. The key is to move them out of scripts and shared folders, then monitor usage so automation can keep running without creating silent standing access across production systems.
Why This Matters for Security Teams
Machine credentials in plant automation are not just technical secrets, they are operational authority. Service accounts, certificates, API keys, and tokens often sit behind PLC gateways, historians, MES integrations, and maintenance tooling, which means a single over-privileged credential can affect safety, uptime, and product quality. Current guidance from the OWASP Non-Human Identity Top 10 and the NIST Cybersecurity Framework 2.0 both point toward stronger identity inventory, least privilege, and continuous monitoring, but plant environments add long-lived tooling and fragile availability constraints.
That makes governance harder than simply rotating secrets on a schedule. Teams must know which identity belongs to which machine, who owns it, where it is used, and what happens when it expires. The practical challenge is that many industrial workflows still depend on embedded credentials in scripts, HMIs, and vendor integrations, so removal must be staged carefully to avoid downtime. In practice, many security teams discover credential sprawl only after a maintenance outage or incident response exercise exposes how many production systems still trust shared access paths.
How It Works in Practice
Effective governance starts with an inventory that treats machine credentials as assets with business owners, technical owners, and defined purpose. The first step is to classify each identity by system, environment, and criticality, then replace undocumented usage with explicit approvals and expiry rules. NHI research on the Secret Sprawl Challenge shows why this matters: secrets frequently spread across scripts, shared folders, and ad hoc support channels, which makes revocation unreliable.
From there, security teams should move toward short-lived credentials where the environment allows it. That means issuing tokens or certificates just in time, binding them to workload identity, and revoking them automatically when the task ends. For plant automation, the best pattern is often a stepwise migration: keep the production process running, insert a credential broker or vault in front of the existing integration, then progressively remove static secrets from endpoints. The Ultimate Guide to NHIs the Static vs Dynamic Secrets explains why dynamic secrets reduce the blast radius when automation is compromised.
- Assign every machine credential to a named owner and a named system.
- Set expiry, rotation, and revocation rules based on operational criticality.
- Prefer workload identity over shared passwords or shared certificates.
- Monitor use patterns so dormant credentials can be disabled safely.
- Separate break-glass access from routine automation access.
For controls and auditability, align the program to NIST SP 800-53 Rev 5 Security and Privacy Controls for account management, access enforcement, and audit logging. These controls tend to break down in plants with vendor-managed systems that cannot support centralized identity brokers or frequent certificate renewal because uptime constraints override redesign timelines.
Common Variations and Edge Cases
Tighter credential governance often increases maintenance overhead, so teams have to balance resiliency against operational change windows. That tradeoff becomes more visible in brownfield plants, legacy SCADA stacks, and vendor appliances that only support static passwords or manually imported certificates. In those environments, best practice is evolving rather than settled: some teams enforce network segmentation and compensating monitoring first, then phase in vault-backed secrets later.
Another edge case is shared automation across multiple sites. A single service account used by several lines or plants makes incident response simpler at deployment time but far riskier during compromise, because revocation can interrupt unrelated production flows. The right response is not always immediate elimination; sometimes it is to scope the credential more narrowly, split duties by function, and add anomaly detection around command frequency, source host, and time of use. NHIMG has documented how exposed machine secrets can be weaponized quickly in the Shai Hulud npm malware campaign, which is a useful reminder that once a credential leaves the plant boundary, attackers move fast.
Where modern identity tooling is available, use policy-based access decisions and short-lived issuance rather than standing trust. Where it is not, establish clear exceptions, compensating monitoring, and a dated retirement plan. There is no universal standard for this yet, but the direction is clear: fewer embedded secrets, more ownership, and faster revocation.
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, NIST SP 800-63, NIST Zero Trust (SP 800-207) and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-03 | Covers secret rotation and lifecycle governance for machine credentials. |
| NIST CSF 2.0 | PR.AC-4 | Least privilege access management fits plant automation credential governance. |
| NIST SP 800-63 | AAL2 | Credential assurance and token strength matter for workload authentication. |
| NIST Zero Trust (SP 800-207) | SP 2 | Zero trust supports continuous verification of machine-to-machine access. |
| NIST AI RMF | AI RMF helps structure governance, accountability, and monitoring for autonomous automation. |
Use strong authentication and verifiable issuance for machine identities that control production systems.
