What should security teams do when human, machine, and agentic identities all share the same trust paths?

One trust path should mean one governance model

When people, workloads, and agents can all move through the same trust paths, the security problem is no longer separate account types. It is one delegation problem: who can act, under what proof, for how long, and with what limits. If that is not governed consistently, teams end up with duplicated approvals, hidden reuse, and revocation gaps that attackers or automation can exploit.

That is why a shared trust path should be treated as a shared control surface. A human session, a service credential, and an agent token may look different operationally, but if they can all reach the same downstream resource, they need the same ownership logic and the same standard for re-validating access before action.

The practical consequence is that “who owns this?” matters more than “what type of identity is it?” A control that only reviews one population, such as users or service accounts, will miss cross-population movement when delegation is passed from one actor to another without a fresh trust decision.

Where shared trust paths break down

The first failure mode is reuse. Once credentials, tokens, or delegated grants are reused across people and systems, blast radius grows because a compromise in one path can silently become access in another. This is especially dangerous when the reuse is operationally convenient, because the reuse often survives longer than the original business need.

The second failure mode is stale authority. A trust path that was valid when created can remain technically valid after the business context changes, even though the person, workload, or agent no longer needs it. That creates a durable access path that may never be exercised legitimately again, yet still exists for misuse or lateral movement.

The third failure mode is ambiguous accountability. If an agent acts using a human-approved workflow, teams sometimes treat the decision as human-owned, while the actual action path is machine-mediated. The result is weak attribution, inconsistent revocation, and a false sense that the right control already exists because some part of the path was approved.

How to govern shared trust paths in practice

Start by defining the trust path itself as the object of control, not just the account or token. Map each path from original actor to downstream resource, then record where delegation occurs, where approval occurs, and where a new trust decision should be required. That map is the only way to see when one path is being reused across multiple identity types.

Next, make ownership explicit. A trust path should have a named business owner and a technical owner who can answer for approvals, expiry, and revocation. Where an agent can act on behalf of a person or service, agent identity and delegation should be governed as lifecycle state, not as an informal implementation detail.

Then reduce standing reach wherever the path crosses identity boundaries. Zero trust for AI agents is a useful pattern here because it forces per-action verification, removes standing privilege, and makes policy decisions visible at the point of use. That same principle helps when a service credential and a human session can both land on the same tool or API.

Finally, make revocation operationally real. If a trust path can outlive the business reason for it, then offboarding, role change, token expiry, and secret rotation all need to hit the same path inventory. Observability and incident response for AI agents matter because you cannot revoke what you cannot attribute, and you cannot attribute what you do not log.

Risk and Threat Considerations

Shared trust paths create a compact attack surface because compromise rarely stays in one category. A stolen human session, over-scoped service credential, or abused agent delegation can all become the same downstream access problem once the path converges on the same resource. That makes reuse, long-lived grants, and weak revocation especially attractive to attackers.

Failure mechanism: The control fails when the organisation treats different identity forms as separate governance domains, so a delegated path survives after the original context changes or after one actor in the chain is compromised.

Impact: Attackers or malicious insiders can inherit access across people, workloads, and agents, then move laterally with less friction, weaker attribution, and a much larger blast radius than the original credential or approval suggested.

Practitioner Guidance

What to prioritise: Build one authoritative inventory of trust paths, not separate lists for users, services, and agents. If the same downstream resource can be reached through more than one identity type, treat that as a single high-value path and review it first.

What to verify: Confirm that every path has an owner, an expiry or review point, and a revocation mechanism that actually removes downstream access rather than only disabling the front-door identity. Test a sample end to end; if the path still works after “revocation,” the control is incomplete.

Common mistake: Teams often rotate the secret but leave the delegation model untouched. That fixes the symptom, not the path, and the next token, approval, or agent action may restore the same exposure.

Practitioner takeaway: When trust paths are shared, the right unit of control is the delegated relationship itself. Secure the path, not just the credential, or governance will always lag behind how access actually moves.

Related resources from NHI Mgmt Group

• How should security teams govern non-human identities at scale?
• How should security teams govern non-human identities for compliance?
• How should security teams govern non-human identities in Salesforce?
• How should security teams run access reviews for non-human identities?