How should utilities phase out default credentials in OT systems?

What utilities are actually phasing out when they remove default credentials?

Default credentials are not just a weak password problem. In OT, they often represent shipped vendor logins, inherited installer accounts, shared maintenance access, or unchanged factory settings that survive commissioning. Phasing them out means eliminating any credential path that multiple sites, devices, or teams still treat as a convenient baseline.

The first practical step is to distinguish device access that is truly unique from access that is only “customised” on the surface. If the same login still works across a fleet, or if a vendor-issued account remains active after handover, the organisation has not really removed the default, it has renamed it.

This matters because OT environments tend to keep old access paths alive for reliability and remote support. Utilities need to treat defaults as lifecycle debt, not just a login issue, so the replacement pattern has to include ownership, traceability, and a path to reset access when the original shared secret is lost or suspected compromised.

What a safe replacement pattern looks like in OT environments

A safe replacement pattern starts with inventory, then moves to credential replacement, then to recovery design. The target state is each device or controller having a uniquely owned credential set, a recorded owner, and a recovery process that does not depend on the factory password, a shared spreadsheet, or a technician memory shortcut.

That usually means replacing shared defaults with individually assigned credentials, disabling unnecessary remote accounts, and making the reset path independent of the original secret. Where possible, the credential should be tied to a managed lifecycle so it can be rotated, revoked, or reissued without a site outage or a manual vendor escalation.

Utilities should also align the change with maintenance windows and fail-safe operating assumptions. Some OT assets can tolerate rapid credential changes; others need staged replacement because authentication changes can disrupt remote diagnostics, historian access, or engineering workflows if dependencies are not mapped first.

Why phasing out defaults is an access-control project, not just an IT clean-up

Default credential removal is really about shrinking the number of easy entry points before broader access redesign begins. It is one of the few changes that can materially reduce exposure without waiting for a full OT IAM overhaul, because a known default is a standing invitation even when the rest of the environment is segmented.

For utilities, the hardest part is often not setting a new password, but proving the old one is gone everywhere it mattered. That includes field devices, embedded controllers, engineering laptops, vendor service channels, backup images, lab units, and any cloned configurations that may reintroduce the same default later.

Once the immediate defaults are removed, the next decision is whether access is governed centrally or left device by device. The more fragmented the fleet, the more important it becomes to standardise ownership, recovery, and exception handling so that future credential changes do not recreate the same shared-secret risk.

Risk and Threat Considerations

Default credentials are attractive because they are low-cost, repeatable, and often work on exposed or poorly monitored OT assets. If one default remains in service, an attacker or unauthorised insider can use it as a foothold for reconnaissance, remote manipulation, or lateral movement into more sensitive control segments.

Failure mechanism: Shared or vendor-default secrets persist across devices, images, or maintenance accounts, then survive handover, cloning, or emergency recovery, creating a reusable access path that defenders may assume has already been retired.

Impact: The result can be unauthorised access to operational assets, loss of trust in remote support paths, and a much larger recovery effort if the same secret is embedded in multiple systems or backup processes.

Practitioner Guidance

What to prioritise: Start with externally reachable OT assets, vendor-supported devices, and anything that still uses a shared factory login. Those are the highest-value footholds because they are easiest to discover and hardest to justify keeping.

What to verify: Confirm that the new credential is truly unique per asset or per role, that the old default no longer works, and that recovery does not require reusing the original factory secret. If a reset path still depends on the default, the transition is incomplete.

Common mistake: Utilities often replace a known default with another shared password and call the problem solved. That reduces visibility, but it does not remove the blast radius or the operational dependence on one secret.

Practitioner takeaway: Treat default credential removal as the first control boundary in OT access hardening, because the real security gain comes from breaking shared access patterns and proving you can recover without reintroducing them.

Related resources from NHI Mgmt Group

• What happens when water utilities expose remote systems with default or weak credentials?
• How do organisations reduce the dwell time of exposed credentials at scale?
• How can organizations manage unauthorized agents in their systems?
• How should organisations stop auto-sync from turning desktops into repositories of credentials?