Why do NHI and service accounts complicate zero trust and PAM?

Why This Matters for Security Teams

NHI and service accounts complicate zero trust and PAM because they rarely behave like human users. They are often embedded in pipelines, run continuously, and need machine-to-machine access without interactive approval. That means the usual assumptions behind session-by-session control, manual review, and user-centric MFA do not hold. The result is not just more identities, but more persistent access paths that must be governed with lifecycle discipline.

Zero trust still applies, but the policy surface changes. NIST’s NIST SP 800-207 Zero Trust Architecture makes continuous verification central, and NHIMG research shows why this matters in practice: Ultimate Guide to NHIs reports that 97% of NHIs carry excessive privileges, while only 5.7% of organisations have full visibility into their service accounts. Without visibility, PAM becomes a vault for dormant risk rather than a control plane.

That is why teams should treat NHI governance as part of the zero trust design itself, not as an after-the-fact exception process. In practice, many security teams encounter excessive NHI privilege only after a breach, rather than through intentional review.

How It Works in Practice

The practical answer is to manage NHI access as a workload lifecycle, not as a human access event. Start by inventorying service accounts, API keys, certificates, and tokens, then map each identity to a business service, owner, and trust boundary. From there, apply least privilege at the workload level, issue short-lived credentials where possible, and rotate or revoke anything persistent on a defined schedule. This aligns with NIST Cybersecurity Framework 2.0 functions for governance, protection, and response.

PAM for NHIs is most effective when it controls issuance, use, and offboarding rather than only storing secrets. That means approval workflows for standing credentials, session constraints for privileged automation, and service ownership for every identity. NHIMG’s Top 10 NHI Issues and Ultimate Guide to NHIs — Lifecycle Processes for Managing NHIs both stress that offboarding and rotation are where controls fail most often. The Entro Security findings in the 2025 State of NHIs and Secrets in Cybersecurity are especially telling: 91% of former employee tokens remain active after offboarding, and 44% of NHI tokens are exposed in the wild.

• Use just-in-time issuance for privileged automation whenever the workload can tolerate it.
• Prefer workload identity over shared secrets so access can be tied to a specific service instance.
• Enforce rotation and expiration with policy, not with informal reminders.
• Log secret use, not just secret creation, so abuse can be detected.

These controls tend to break down when legacy batch jobs and third-party integrations require static secrets that cannot be refactored quickly.

Common Variations and Edge Cases

Tighter control often increases operational overhead, so organisations have to balance security gain against service availability and release velocity. That tradeoff is especially visible in brownfield environments, where shared accounts, hard-coded credentials, and vendor-managed integrations are already embedded in production. Current guidance suggests phasing control in rather than forcing a full redesign overnight.

One common edge case is the overused service account. If multiple applications share the same identity, PAM can still record access, but it cannot clearly attribute intent or enforce meaningful separation of duties. Another is long-lived automation in CI/CD or infrastructure tooling, where rotation windows can disrupt deployment if ownership is unclear. This is why NHIMG’s 52 NHI Breaches Analysis is so instructive: compromise is often amplified by persistence, duplication, and weak offboarding, not by a single missing control.

For teams building a zero trust programme, the most realistic path is to combine RBAC for coarse scoping, JIT for privilege elevation, and continuous review for secrets and sessions. Where organisations use SPIFFE or similar workload identity systems, the identity primitive becomes the workload itself rather than a reusable password. That is a strong pattern, but there is no universal standard for every environment yet, especially where agents, legacy services, and vendor systems collide. In those environments, PAM and zero trust fail most often when no one can prove who owns the identity or when it should stop working.

Related resources from NHI Mgmt Group

• Why do Active Directory service accounts complicate zero trust programs?
• Why do non-human identities complicate zero trust architecture?
• Why do NHIs complicate zero trust and least privilege efforts?
• Why do non-human identities increase zero trust risk?