When do standing credentials become a serious OT risk?

Why Standing Credentials Become an OT Risk

Standing credentials turn dangerous in OT when they outlive the task, the shift, or the maintenance window. In environments where engineering workstations, PLCs, historians, remote access gateways, and vendor support channels are all tied together, a single long-lived credential can become a path from routine access to plant-wide disruption. Current guidance from the OWASP Non-Human Identity Top 10 and the NIST Cybersecurity Framework 2.0 is clear on least privilege, but OT adds a harder constraint: access must also respect operational timing and safety boundaries. That is why standing access is not just a policy issue, it is an exposure window.

NHIMG research shows how quickly exposed credentials can be operationalised. In the LLMjacking: How Attackers Hijack AI Using Compromised NHIs report, attackers attempted access to publicly exposed AWS credentials in an average of 17 minutes. The lesson transfers cleanly to OT: if credentials are valid long enough to be copied, reused, or shared across vendors, they are valid long enough to be abused. In practice, many security teams discover the problem only after a maintenance credential has become the easiest route into systems that were never meant to be permanently reachable.

How OT Teams Should Reduce the Risk in Practice

The practical answer is to stop treating OT access as a permanent entitlement and start treating it as a bounded operational event. For human access, that means using PAM, JIT elevation, and strong session recording so a technician gets the minimum access needed for the maintenance task and loses it when the task ends. For machine and service access, the better model is short-lived secrets and workload identity, so a process proves what it is with cryptographic identity instead of holding a password that can be reused later. The Ultimate Guide to NHIs — Static vs Dynamic Secrets is a useful reference for this shift, and the Guide to the Secret Sprawl Challenge shows why unmanaged credentials tend to outlive the processes that created them.

• Use time-bound access for vendors, contractors, and maintenance staff, not standing VPN or jump-host accounts.
• Bind credentials to a specific asset, ticket, or change window so access expires when the work is complete.
• Prefer per-session approval, session capture, and command-level logging for supervisory and engineering systems.
• Replace shared secrets with workload identity where scripts, integrations, or service accounts must act autonomously.
• Review every route that connects IT identity systems to OT endpoints, because a single weak link often defeats the whole control set.

This guidance aligns well with NIST SP 800-63 Digital Identity Guidelines for identity proofing and assurance, but OT environments often need compensating controls because legacy controllers and vendor tools do not support modern token lifecycles. These controls tend to break down when remote support tools require persistent access for emergency troubleshooting because operational urgency overrides revocation discipline.

Common OT Edge Cases and Control Tradeoffs

Tighter access control often increases operational friction, requiring organisations to balance safety, uptime, and recovery speed against the need to remove standing privilege. That tradeoff is real in plants with 24/7 operations, legacy engineering software, or third-party OEM support that was designed around shared accounts. There is no universal standard for this yet, so current guidance suggests documenting exceptions explicitly and revisiting them frequently rather than allowing temporary access to become permanent by default.

One common edge case is break-glass access. It is acceptable for emergency use, but only if the account is isolated, heavily monitored, and subject to after-action review. Another is service connectivity between OT and adjacent systems such as patch management, historians, or data brokers. Those links often need machine identity, not static credentials, because they may run unattended for long periods. The Cisco Active Directory credentials breach is a reminder that even standard enterprise identity material can become a direct entry point when it is reused too broadly, and the same logic applies to OT once credentials are shared across zones.

Where OT governance matures, teams increasingly pair ZTA principles with segmented trust zones and strict expiry rules. Where it does not, standing access survives because “it has always worked” and nobody owns the revocation process. That is the real risk: the credential becomes part of the operating model instead of a temporary exception.

Related resources from NHI Mgmt Group

• What makes idle secrets such a serious NHI risk?
• When does secret exposure become a broader identity risk?
• When do service accounts become a higher risk than ordinary user accounts?
• Why do non-human identities create more audit risk than human accounts?