Shared credentials break accountability and make privilege control difficult to enforce. If multiple engineers, contractors, or vendors can reuse the same access, it becomes hard to know who changed what, when, or why. The result is weaker traceability, higher misuse risk, and more difficulty proving compliance when incidents or audits occur.
Why Shared Credentials Break OT Maintenance Accountability
shared credentials collapse the link between an action and a person. In OT maintenance, that means a change record, alarm acknowledgement, firmware update, or configuration adjustment no longer points to a specific engineer, contractor, or vendor. Once the same login is reused across shifts or suppliers, traceability becomes a process guess instead of an evidence-backed record.
This is why shared access is especially damaging in maintenance windows, where actions are often urgent, disruptive, and performed under pressure. If the environment cannot distinguish one operator from another, it also becomes much harder to reconstruct the sequence of events after a fault, safety issue, or unauthorised change.
Why Privilege Control Gets Weak Fast
Shared credentials also undermine privilege control. A single reused account tends to accrete permissions because it must serve multiple people and tasks, which pushes teams toward broad access rather than task-specific access. Over time, that creates a standing privilege problem: the credential can be used by more people, for more systems, for longer than originally intended.
In OT, that matters because maintenance access is often a bridge into sensitive engineering workstations, HMI interfaces, PLC-related tools, or remote support channels. If the same secret is used by multiple parties, revocation becomes blunt, temporary access is hard to scope, and it is difficult to prove that only the minimum necessary access was available for the maintenance activity.
Why Incidents and Audits Become Harder to Prove
When shared credentials are used, incident response loses a clean evidence trail. Investigators can see that an account was used, but not whether the action came from a vendor, an internal technician, or an unauthorised user who learned the password. That makes root-cause analysis slower and containment decisions less certain.
Compliance reviews face the same problem. Many OT programmes need to show who accessed which system, when the access occurred, and why it was justified. Shared credentials weaken that proof, because the audit record may show activity, but not attributable identity. The control problem is not only security, it is also evidentiary integrity.
Risk and Threat Considerations
Shared maintenance credentials create a high-value choke point for misuse, especially where remote support, contractors, or cross-shift operations are involved. If the credential is leaked, reused, or copied, an attacker inherits a legitimate access path that can be difficult to distinguish from authorised maintenance activity.
Failure mechanism: a single reusable secret removes individual attribution, expands the blast radius of compromise, and makes revocation or forensic separation of actions unreliable.
Impact: teams lose confidence in change records, malicious activity can hide inside routine maintenance, and organisations may struggle to defend operational decisions during an incident review or audit.
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 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | Shared OT credentials are secret material whose reuse increases exposure and misuse risk. |
| NHI-05 — Overprivileged NHI | Shared access commonly forces broad permissions across multiple maintainers. | |
| NHI-07 — Long-Lived Secrets | Shared credentials tend to persist across shifts, vendors, and maintenance cycles. | |
| Recommendation — Eliminate shared maintenance secrets and rotate any exposed credential immediately. Scope access to the minimum role needed for each maintenance task. Replace persistent shared credentials with short-lived, individually attributable access. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Shared credentials are an authenticator lifecycle and reuse problem. |
| AU-2 — Event Logging | OT maintenance accountability depends on logs that tie actions to a unique actor. | |
| AC-6 — Least Privilege | Shared accounts commonly expand access beyond task-specific need. | |
| Recommendation — Manage authenticator issuance, rotation, and revocation so each user remains separately accountable. Log maintenance actions with identity, time, and target system details. Restrict maintenance access to the minimum permissions required for the job. | ||
| CIS Controls v8 | CIS-5 — Account Management | Shared credentials are an account governance failure that impairs accountability. |
| CIS-6 — Access Control Management | Maintenance access must be separated, reviewed, and bounded to preserve control. | |
| Recommendation — Assign unique accounts and revoke shared access paths wherever possible. Enforce individual access controls and review exceptions on a schedule. | ||
Practitioner Guidance
What to verify: confirm that every maintenance path has an attributable identity, even if access is time-bound or vendor-assisted. If a login can be reused by more than one person, treat that as a governance gap, not just an access convenience.
Decision rule: if the account can touch production OT assets, require a mechanism that separates people, sessions, or approvals so the organisation can answer who acted, what they did, and under whose authority. Shared access may still exist in legacy environments, but it should be treated as an exception with explicit compensating controls.
Practitioner takeaway: the main loss from shared OT maintenance credentials is not only weaker security, it is the collapse of trustworthy attribution, which then weakens privilege enforcement, incident reconstruction, and compliance evidence at the same time.
Related resources from NHI Mgmt Group
- What breaks when shared proxy credentials are used for AI workloads?
- What breaks when manufacturing teams rely on shared credentials and legacy authentication in OT environments?
- How should security teams govern API keys used for generative AI access?
- How do organisations reduce the dwell time of exposed credentials at scale?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 26, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
