What happens when critical infrastructure relies on local accounts and shadow access instead of centrally governed identities?

When critical infrastructure depends on local accounts and shadow access, organisations lose control over who can reach essential systems and why. That creates hidden exposure, especially if an account is orphaned or privileges are broader than necessary. In practice, attackers can exploit those unmanaged paths to gain a foothold, move laterally, and trigger incidents that are harder to investigate and contain.

When critical infrastructure leans on local accounts and shadow access, identity governance stops being a source of control and becomes a source of uncertainty. Each unmanaged login path can bypass central policy, logging, and approval, which weakens attribution and makes it harder to prove who had access at a given moment. That matters most where uptime, safety, and recovery depend on knowing exactly which identities can act on a system.

Shadow access also tends to accumulate quietly during maintenance, vendor support, emergency troubleshooting, and legacy integration work. Over time, that creates hidden privilege that is easy to forget and difficult to review. NHI Management Group’s research on the Ultimate Guide to NHIs shows how often organisations lose visibility into service and machine access once credentials are allowed to drift outside governed lifecycle processes. In practice, many teams discover these paths only after an outage, an audit request, or a compromise has already exposed them.

How It Works in Practice

Central identity governance works because access can be issued, scoped, logged, reviewed, and revoked from a common control plane. Local accounts and shadow access break that model by distributing authority across devices, engineers, vendors, and emergency exceptions. In critical infrastructure, that often means passwords or keys exist on individual hosts, in scripts, in support tooling, or inside undocumented break-glass procedures, while no single team can answer basic questions about ownership, expiry, or effective privilege.

The operational problem is not just excess access. It is fragmented trust. A local administrator account on a plant system, a shared vendor login on a controller, or a long-lived credential embedded in a maintenance tool may still work long after the original business need has changed. That creates three practical failures: access cannot be reliably revoked, activity cannot be cleanly attributed, and lateral movement becomes easier because unmanaged credentials often outlive the systems and people that introduced them. The issue is especially acute where legacy operational technology was never designed for modern identity federation or short-lived authentication.

Local accounts often bypass central joiner-mover-leaver processes, so offboarding does not remove their effective access.
Shadow access often survives because it is treated as operational convenience rather than governed entitlement.
Shared or static credentials obscure accountability, which weakens incident response and post-incident forensics.
Exception paths become attack paths when maintenance access is broader than the minimum needed.

The OWASP Non-Human Identity Top 10 is useful here because it frames unmanaged machine and service access as a first-class security problem, not just an administration issue. A closely related operational pattern is the overuse of static credentials, which the Ultimate Guide to NHIs — Lifecycle Processes for Managing NHIs treats as a lifecycle failure rather than a one-time configuration choice. These controls tend to break down when legacy systems cannot support federation or when emergency support workflows are left permanently in place.

Common Variations and Edge Cases

Tighter identity governance often increases operational friction, so organisations have to balance control with the realities of uptime, safety, and vendor support. Not every local account is automatically wrong, but every exception should have a defined owner, a reason for existing, and a removal condition. The hard part is distinguishing a true recovery pathway from an access path that has simply never been retired.

Best practice is evolving for environments that cannot fully federate, especially industrial and embedded systems. In those cases, teams often need compensating controls such as isolated jump access, unique credentials per device, stronger logging, and frequent access review. The CISA cyber threat advisories and the NIST Cybersecurity Framework 2.0 both support the broader principle that access control, monitoring, and recovery planning need to work together rather than as separate programmes.

Where organisations still rely on shadow access, the main edge case is not whether the account is technically valid. It is whether the account is still defensible as a current business requirement. If the answer is unclear, the risk is already material.

Risk and Threat Considerations

Critical infrastructure that depends on local accounts and shadow access has a material exposure problem: access becomes difficult to inventory, difficult to revoke, and difficult to attribute. That raises the likelihood of persistent unauthorized access, especially where privileged accounts are shared, long-lived, or exempt from central governance.

Failure mechanism: Adversaries and insiders can abuse undocumented credentials, stale support logins, or privileged local accounts to bypass centralized controls, preserve access after a compromise, and move laterally across systems that should have been isolated. Weak account ownership and incomplete logging make those paths harder to detect and contain.

Impact: The result can be loss of control over essential systems, delayed incident response, broader blast radius, and incomplete forensic visibility. In infrastructure environments, that can turn a single unmanaged access path into an outage, safety event, or prolonged recovery effort.

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 MITRE ATT&CK address the attack and risk surface, while NIST CSF 2.0 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-01 — Inventory and Ownership	Local and shadow accounts are unmanaged non-human access paths.
	NHI-03 — Secrets and Credential Management	Shadow access often persists through static or shared credentials.
	NHI-05 — Privilege and Access Scope	Ungoverned local accounts frequently carry excessive privilege.
Recommendation — Inventory every non-human account and assign a named owner with removal authority. Rotate and revoke exposed credentials and replace shared access with unique identities. Reduce account scope to least privilege and remove standing administrative access.
NIST CSF 2.0	PR.AA-01 — Identity and Access Management	Central governance is an identity assurance and access control issue.
Recommendation — Centralize access approval, review, and revocation for critical infrastructure identities.
CIS Controls v8	6 — Access Control Management	This topic centers on controlling and reviewing privileged access paths.
Recommendation — Remove unmanaged accounts and enforce regular access review for privileged systems.
MITRE ATT&CK	T1078 — Valid Accounts	Attackers commonly abuse legitimate but unmanaged accounts for access persistence.
Recommendation — Hunt for legitimate account misuse and alert on anomalous use of local or shared logins.

Practitioner Guidance

What to prioritise: Treat every local or shadow account on critical systems as an inventory and ownership problem before it is a password problem. The immediate question is not whether the account is currently being used, but whether the organisation can explain why it exists, who owns it, and how it will be removed.

Decision rule: If an account can reach production infrastructure and is not governed by normal identity lifecycle controls, it should be treated as a high-risk exception until proven otherwise. Preserve it only when there is a documented operational dependency and a compensating control path for review, logging, and revocation.

What to verify: Confirm that every exception has unique accountability, time-bound access where possible, and a tested revocation path. Also verify that incident response can still reconstruct who used the account, from where, and for what purpose; if that evidence is not available, the control is not mature enough to trust.

Practitioner takeaway: The real objective is not to eliminate every local account immediately, but to make every remaining exception observable, attributable, and removable before it becomes the only working path into critical infrastructure.