How should utilities reduce OT exposure while preparing for CIP-015-2?

Why This Matters for Security Teams

CIP-015-2 pushes utilities to narrow OT exposure in a way that is auditable, repeatable, and defensible during operations. The practical issue is not only perimeter hardening, but reducing unnecessary identity paths into control environments where a single over-permissive account can become a pathway to broader disruption. NHIMG’s Ultimate Guide to NHIs — Why NHI Security Matters Now notes that 90% of IT leaders say properly managing NHIs is essential for a successful zero-trust implementation, which fits the direction utilities are moving.

For OT teams, the risk is not hypothetical. A remote access path, shared credential, vendor tunnel, or unmanaged service account can become a persistence point that bypasses segmentation and weakens evidence quality during an incident review. This is especially important where operational uptime pressures have historically justified broad exceptions. In practice, many security teams encounter OT overexposure only after a maintenance path, vendor session, or compromised secret has already been used to move beyond its intended scope.

How It Works in Practice

The most effective approach is to treat access as a task-specific control, not a permanent entitlement. That means identifying who or what needs access, for which asset, under what condition, and for how long. For human users, utilities typically combine MFA, device posture checks, and tightly scoped role assignments. For non-human access, the stronger model is ephemeral identity and short-lived secrets rather than static credentials that sit dormant until abused.

In OT environments, current guidance suggests mapping access around zones, conduits, and operational roles so that a technician, integrator, or monitoring tool only reaches the assets needed for the current job. Where feasible, this should be paired with just-in-time approval and automatic revocation when the task ends. That creates cleaner evidence for compliance teams and limits standing pathways into critical control systems. The implementation logic aligns with NIST’s Zero Trust Architecture, which emphasizes continuous verification and least privilege, rather than one-time trust.

For utilities preparing for CIP-015-2, the operational sequence usually looks like this:

• Inventory all OT-adjacent identities, including service accounts, vendor accounts, jump hosts, and automation accounts.
• Remove shared credentials and replace them with named, traceable access where possible.
• Enforce MFA and device compliance on every interactive path into OT support systems.
• Use short-lived credentials and session controls for maintenance, engineering, and remote support tasks.
• Log access with enough context to show who accessed what, when, from where, and for what purpose.

For identity primitives, the direction of travel is toward workload identity and policy evaluation at request time, rather than reliance on static network trust. Standards such as SPIFFE are relevant when the access need is machine-to-machine and must be cryptographically bound to workload identity. These controls tend to break down in highly legacy OT sites where vendor tooling, unsupported devices, and flat exception lists still force long-lived shared access.

Common Variations and Edge Cases

Tighter OT access controls often increase operational overhead, so utilities have to balance resilience against maintenance friction. The hardest environments are those with legacy PLCs, unmanaged vendor dependencies, or remote substations where authentication options are limited. In those cases, the right answer is usually compensating control plus phased reduction of exposure, not an immediate attempt to force a modern identity stack onto unsupported equipment.

There is no universal standard for this yet, but best practice is evolving toward stronger session accountability, shorter credential lifetimes, and explicit approval workflows for elevated access. NHIMG’s 52 NHI Breaches Analysis and Schneider Electric credentials breach both reinforce the same lesson: excessive or unmanaged identities turn access paths into attack paths. For utilities, the practical priority is to reduce standing exposure first, then improve monitoring depth on the remaining paths. In segmented OT networks with multiple third-party maintainers, identity sprawl and exception handling usually become the weakest point long before the control network itself is technically breached.

Related resources from NHI Mgmt Group

• How should security teams reduce exposure in remote access infrastructure?
• How should security teams reduce exposure in cloud-routed ZTNA architectures?
• When does secret exposure become a broader identity risk?
• How can organisations reduce the blast radius of compromised agent identities?