How should security teams handle legacy network devices in NHI governance?

Security teams should treat legacy network devices as identity-bearing assets with ownership, rotation, and offboarding requirements. If a device still relies on static credentials or shared admin access, it belongs in the same control plane as other NHIs. That means inventorying it, limiting its reach, and retiring it where possible.

Why Legacy Network Devices Belong in NHI Governance

Legacy routers, switches, firewalls, VPN concentrators, and industrial gateways often outlive the credential model they were built with. If a device still uses shared admin passwords, static SNMP communities, or vendor defaults, it is acting as a non-human identity with persistent authority. The governance problem is not the hardware age alone, but the fact that the device can authenticate, authorize, and reach other systems long after its original trust assumptions have expired.

This is where teams usually miss the control boundary. They treat the device as infrastructure and its secrets as an operations detail, even though those secrets can enable lateral movement, configuration tampering, or silent persistence. NHI governance is designed for exactly this class of risk, especially when credentials are not rotated and access paths are poorly observed. The Top 10 NHI Issues research highlights that lack of credential rotation is cited as the top cause of NHI-related attacks by 45% of organisations, reinforcing why static access on legacy devices should be treated as a material control failure. Current guidance also aligns with NIST Cybersecurity Framework 2.0 and NIST SP 800-207 Zero Trust Architecture, both of which emphasize managed identity, least privilege, and continuous verification.

In practice, many security teams encounter legacy device identity exposure only after a change window, audit finding, or breach investigation has already exposed it.

How to Govern Legacy Devices as Identity-Bearing Assets

Start by inventorying every legacy device that can authenticate to a management plane, peer system, or upstream service. Record ownership, admin pathways, credential type, rotation method, network reach, and whether the device can be retired or isolated. Then classify it as an NHI if it possesses any credential that can be used independently of a human operator. That classification matters because it moves the device into lifecycle management, not just asset management.

From there, apply the same discipline used for other NHIs. Bind each device to an owner, replace shared credentials with unique identities where the platform allows it, and set explicit rotation intervals for all secrets. If the device cannot support modern identity primitives, compensate with compensating controls: narrow network access, dedicated management VLANs, jump hosts, PAM, and RBAC enforced on the console or surrounding control plane. The Ultimate Guide to NHIs — Lifecycle Processes for Managing NHIs is useful here because the lifecycle view makes offboarding and renewal as important as provisioning. For broader context on how devices fit the identity model, see the Ultimate Guide to NHIs — What are Non-Human Identities.

• Replace shared admin access with unique, named accounts or device-bound credentials wherever possible.
• Use JIT elevation for administrators instead of permanent standing access to legacy management planes.
• Rotate passwords, API keys, and certificates on a documented schedule, with emergency revocation playbooks.
• Restrict outbound and east-west reach so a compromised device cannot become a pivot point.
• Log all authentication attempts and configuration changes into a central monitoring pipeline.

This guidance breaks down in environments where firmware is frozen, vendor support has ended, and the device cannot accept unique credentials or modern logging.

When Legacy Constraints Force Compensating Controls

Tighter device isolation often increases operational overhead, requiring organisations to balance resilience against maintenance complexity. There is no universal standard for this yet, so current guidance suggests treating the device’s limitations as a risk to be reduced, not a justification to leave access unmanaged. The practical tradeoff is that some legacy platforms cannot be modernized without service disruption, especially in OT, branch networking, or embedded appliance fleets.

In those cases, security teams should document the exception, set a retirement date, and apply compensating controls that reduce blast radius. That usually means network segmentation, deny-by-default firewall rules, restricted maintenance windows, console access through PAM, and explicit break-glass procedures with immediate review after use. The 52 NHI Breaches Analysis shows how recurring identity failures turn into repeat incidents when ownership and rotation are weak. The broader Ultimate Guide to NHIs is also a strong reference point for tying exceptions back to lifecycle governance and auditability.

One important edge case is devices that support certificates but not automated renewal. Those should not be treated as fully managed merely because they use PKI. Another is environments with vendor remote support, where shared access may be unavoidable in the short term; in that case, access should be time-bound, monitored, and documented as a risk acceptance. Organisations that wait for a perfect upgrade path usually discover the real exposure during incident response, not during planning.

Related resources from NHI Mgmt Group

• How should security teams use IAST and RASP in NHI governance?
• How should security teams prioritise NHI remediation in cloud environments?
• How should security teams make NHI best practices usable across the business?
• What is the difference between role-based access and API key governance for NHI security?