They often treat shadow access as a visibility problem alone, when it is also a lifecycle and accountability problem. If a contractor tunnel or OEM shortcut is not owned, reviewed, and retired, it becomes permanent privileged exposure. The right response is governance, not just discovery.
Why Security Teams Miss the Real Problem
shadow access in CPS is often spotted as an inventory gap, but the deeper issue is that it creates unmanaged privilege paths that survive long after the original business need has passed. A contractor tunnel, OEM support account, or emergency bypass can look temporary while quietly becoming a standing exception. That is why governance matters as much as discovery, and why lifecycle ownership must be explicit. The broader NHI problem is large enough that only 5.7% of organisations report full visibility into their service accounts, according to the Ultimate Guide to NHIs by NHI Mgmt Group.
Security teams also underestimate how shadow access bypasses normal review paths. These identities are often created outside PAM, outside RBAC design, and outside the ticketing process that would normally trigger offboarding. Once that happens, the problem is not just “can we see it” but “who owns it, what is it allowed to do, and when is it removed.” The OWASP Non-Human Identity Top 10 frames this as an identity risk, not a monitoring-only issue.
In practice, many security teams encounter shadow access only after an audit, outage, or incident has already exposed how long the exception had been active.
How It Works in Practice
In CPS environments, shadow access usually appears through remote maintenance paths, vendor support channels, orchestration bridges, or one-off integrations that were meant to reduce operational friction. The control failure is rarely the tunnel itself. It is the absence of clear identity governance around that tunnel: no named owner, no expiry, no review cadence, and no defined retirement step. Once a path exists, it can outlive the original incident response or commissioning window and become a permanent privileged channel.
Practitioners should treat this as a full NHI lifecycle issue. Current guidance suggests three linked controls: first, register every non-human credential and access path; second, bind each one to a business owner and technical custodian; third, force time-bound review and revocation. That means JIT access where possible, short-lived secrets where permanent credentials are not necessary, and explicit separation between operational convenience and long-term entitlement. The Ultimate Guide to NHIs — Key Challenges and Risks and the 52 NHI Breaches Analysis both show that excessive privilege and weak remediation are recurring failure patterns.
- Use PAM for brokered entry, but do not confuse brokered access with governed access.
- Require intent-based approval for remote actions that exceed normal operating scope.
- Rotate or revoke secrets when vendor work ends, not when someone remembers to clean up.
- Log who approved the path, what it touched, and when it was retired.
These controls tend to break down in brownfield CPS estates where legacy OEM tooling, safety constraints, and mixed IT/OT ownership make automatic revocation difficult.
Where the Guidance Gets Hard in Legacy CPS
Tighter shadow-access controls often increase operational overhead, requiring organisations to balance uptime and vendor responsiveness against reduced exposure. That tradeoff is real in CPS, especially where safety windows are narrow and equipment vendors insist on persistent support channels. Best practice is evolving here: there is no universal standard for every environment, but the direction is clear. Permanent exceptions should become time-boxed, and time-boxed exceptions should become automated where the platform allows it.
Two edge cases matter most. First, emergency access during outages may justify temporary privilege elevation, but only with post-event review and a documented kill switch. Second, service-account sprawl inside OT tooling can hide access that looks “internal” but is effectively third-party exposure. This is where the OWASP Non-Human Identity Top 10 helps teams separate discovery from containment, while the Ultimate Guide to NHIs is useful for turning that insight into lifecycle controls.
The main mistake is assuming that every hidden path is malicious. Some are legitimate, but legitimacy without ownership becomes risk the moment the original purpose changes. In CPS, the safest posture is to assume that any undocumented access path is temporary until proven otherwise.
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 OWASP Non-Human Identity Top 10 address the attack and risk surface, while 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 | Shadow access often persists because secrets are not rotated or revoked on time. |
| OWASP Non-Human Identity Top 10 | NHI-01 | Undocumented tunnels and support accounts create unmanaged identity exposure. |
| NIST Zero Trust (SP 800-207) | PR.AC-4 | Shadow access bypasses least-privilege and continuous verification principles. |
| NIST AI RMF | Accountability and governance are required for autonomous or delegated access decisions. |
Establish ownership, review, and escalation rules for every privileged non-human pathway.
Related resources from NHI Mgmt Group
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on June 7, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
