How do IAM teams know whether zero trust and segmentation are actually working?

Why This Matters for Security Teams

zero trust and segmentation are only meaningful if the environment actually constrains authenticated identities at runtime. For IAM teams, the practical question is not whether policies exist, but whether a service account, workload identity, or API key can still reach sensitive systems after compromise. NIST SP 800-207 Zero Trust Architecture makes clear that trust should be continuously evaluated, not assumed from network location alone.

That distinction matters because NHI abuse often looks “valid” at the identity layer while still being excessive at the access layer. NHI Management Group’s Ultimate Guide to NHIs notes that 97% of NHIs carry excessive privileges, which means many organisations believe they have segmentation when they really have broad, reusable access wrapped in network controls. If a compromised workload can pivot from one zone to another, the control plane is not enforcing least privilege in a way that limits blast radius.

In practice, many security teams discover weak segmentation only after a service account has already moved laterally, rather than through intentional testing of containment and deny-by-default behavior.

How It Works in Practice

IAM teams usually validate zero trust and segmentation by testing three things together: identity scope, path restriction, and failure containment. First, they confirm that the authenticated workload identity is bound to the exact resource set it needs. Second, they verify that the network or service mesh blocks any path outside that scope. Third, they simulate compromise and check whether the blast radius stays inside a small zone. That is the real operational test, not whether an identity can log in.

For workload-centric environments, the best practice is evolving toward cryptographic workload identity and runtime policy decisions. The Guide to SPIFFE and SPIRE is useful here because it frames identity as proof of what the workload is, not just a secret it presents. In parallel, policy engines should evaluate requests in context, using request attributes, service role, and environment state. That aligns with the intent of NIST SP 800-207 Zero Trust Architecture, which emphasises continuous verification.

• Test whether a compromised service account can call only approved APIs, not neighboring systems.
• Validate that east-west traffic is denied by default except for explicit service-to-service paths.
• Check whether short-lived credentials expire before they can be reused across zones.
• Review logs for denied requests that should have been blocked by segmentation, not just observed.

NHIMG research also shows why this matters: the Ultimate Guide to NHIs — Standards highlights that 90% of IT leaders consider NHI management essential to zero trust, yet only 5.7% of organisations have full visibility into service accounts. These controls tend to break down in hybrid and multi-cloud environments because identity policy, network policy, and secrets governance are often enforced by different teams using different control planes.

Common Variations and Edge Cases

Tighter segmentation often increases operational overhead, requiring organisations to balance blast-radius reduction against service reliability and troubleshooting complexity. That tradeoff is real, especially when teams manage legacy apps, dynamic microservices, or multi-cloud estates where identity signals are inconsistent.

Current guidance suggests that segmentation testing should be environment-specific. A flat application tier can make network boundaries look strong on paper while failing under lateral movement. In contrast, service mesh environments can enforce finer-grained policy, but only if workload identities are correctly issued, rotated, and mapped to policy. This is where long-lived credentials and broad allowlists undermine the design.

One useful edge case is third-party and automation access. If external schedulers, CI/CD runners, or backup tools can reach production broadly, segmentation may still “work” for humans while failing for NHIs. The 2024 Non-Human Identity Security Report found that only 19.6% of security professionals are strongly confident in securely managing non-human workload identities, which helps explain why hidden exceptions often linger. There is no universal standard for proving segmentation yet, so teams should treat red-team lateral movement tests, access reviews, and deny logs as complementary evidence rather than a single source of truth.

Related resources from NHI Mgmt Group

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• How do security teams know whether enterprise IAM is actually working?
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