Legacy device identities often predate current lifecycle controls, so their permissions may be stored in formats that modern revocation logic no longer governs. When a platform has multiple entitlement sources, older records can remain active even after the current token is removed. That creates lingering access that is hard to detect through ordinary administration.
Why This Matters for Security Teams
Legacy device identities are risky because they often survive beyond the lifecycle controls that were designed to remove them. In NHI environments, that means access can persist even when a current token is revoked, a certificate is rotated, or an admin believes the device has been decommissioned. The problem is not just excess privilege. It is entitlement drift across systems that do not share a single source of truth.
This is a recurring theme in NHI governance research. NHIMG’s Ultimate Guide to NHIs shows that only 20% of organisations have formal processes for offboarding and revoking API keys, while 71% of NHIs are not rotated within recommended time frames. That is the environment where older device identities stay live long after they should have been retired. The OWASP Non-Human Identity Top 10 also highlights how weak lifecycle controls and secret sprawl turn identity debt into persistent exposure.
For security teams, the operational risk is simple: if a legacy device identity still maps to a valid entitlement, it can be reused, inherited, or forgotten by every control plane that trusts it. In practice, many security teams encounter persistent access only after a decommissioned system has already been abused or rediscovered during incident response.
How It Works in Practice
Legacy device identities usually become persistent because they were created under older provisioning models and then copied into newer platforms without being fully reconciled. A device certificate, service principal, API key, or machine account may remain in an identity store, config file, vault, or CI/CD variable even after the device itself is gone. When multiple entitlement sources exist, revocation may remove one credential path but leave another path intact.
That is why modern NHI governance focuses on the whole lifecycle, not just credential expiry. The practical control set usually includes:
- Inventorying every device identity and mapping it to an owning system, business service, and retirement date.
- Separating authentication from authorisation so a valid identity does not automatically imply lasting access.
- Revoking stale certificates, keys, and token bindings in every authority that can issue or honour them.
- Using short-lived credentials and rotation to reduce the window in which a forgotten identity remains usable.
- Checking entitlement sources in the CMDB, IAM, PAM, secrets manager, and application configuration at the same time.
That approach aligns with NIST’s Cybersecurity Framework 2.0, which treats identity and access governance as an ongoing function, not a one-time admin task. It also matches NHIMG guidance in the Ultimate Guide to NHIs – Key Challenges and Risks, where visibility and offboarding are shown as core failure points. When a legacy identity spans on-prem, SaaS, and pipeline tooling, these controls tend to break down because no single system can prove it is the last remaining source of access.
Common Variations and Edge Cases
Tighter revocation controls often increase operational overhead, requiring organisations to balance faster cleanup against the risk of disrupting legitimate automation. That tradeoff is especially visible when device identities support batch jobs, firmware update paths, or vendor-managed integrations that were not built for frequent credential churn.
There is no universal standard for this yet, but current guidance suggests treating legacy identities differently from active workload identities. If a device cannot support modern rotation or attestation, best practice is to isolate it, constrain it with zero standing privilege, and assign a clear retirement deadline rather than letting it remain in general-purpose access groups. For some environments, especially industrial systems or embedded appliances, revocation may have to be staged because the device cannot re-enrol without downtime.
NHIMG’s Top 10 NHI Issues is useful here because it frames the governance gap as a visibility and lifecycle problem, not just a secrets problem. The hardest cases are inherited identities after mergers, cloned golden images, and old service accounts still trusted by downstream apps. Those environments need a reconciliation process, not just periodic password changes, because the access path itself may already be embedded in multiple control planes.
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 CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 | Legacy identities persist when inventory and lifecycle controls are missing. |
| NIST CSF 2.0 | PR.AC-4 | Persistent device access is an access governance and least-privilege issue. |
| OWASP Non-Human Identity Top 10 | NHI-03 | Stale device credentials often survive because rotation and revocation are incomplete. |
Use short-lived credentials and automate rotation and revocation for device identities.
