What should security teams do when model-driven access uses shared credentials?

Why shared credentials change the security problem

Shared credentials turn model-driven access from an attributable action path into a pooled trust path. That matters because the control objective is not just whether the request is authenticated, but whether the action can be traced, constrained, and revoked without affecting unrelated users or automations. Once multiple actors share the same secret, ownership, intent, and blast radius all become harder to distinguish.

This is why a shared credential should be treated as a governance smell, not a convenience feature. If the model is acting through the same credential as humans or other automations, teams lose the ability to prove who approved the access path, what the model was allowed to do, and which actions should be stopped first during an incident.

For the underlying identity pattern, NHI guidance on human vs non-human identity is useful because it separates ownership and lifecycle questions from simple connectivity questions.

What security teams should require instead

Security teams should replace shared credentials with a governed identity flow that names the owner, scopes the tool, and defines the allowed action path. The model may still access systems, but the access should be issued through an identifiable identity, with explicit boundaries around what it can read, change, approve, or trigger.

That means the security design should prefer distinct credentials, delegated access, or short-lived tokens where possible, and should bind each tool pathway to a responsible business or technical owner. If a team cannot answer who owns the access, who can revoke it, and what the model is allowed to do at runtime, the access pattern is not ready for production use.

For teams working through credential design and replacement patterns, the API Key Management Guide and Secrets Management Guide both reinforce the same practical point: secrets are not a substitute for governance, and long-lived shared secrets are especially poor foundations for controlled access.

Where the access path is machine-to-machine, the trust model should be explicit rather than inherited from the credential itself. A shared secret tells you only that someone knew the secret, not that the request was appropriate for the model, the task, or the environment.

How to handle high-impact actions and runtime review

High-impact actions should not be auto-approved just because the caller is a model. Teams should classify actions by consequence, then require runtime review or step-up approval for anything that can change permissions, move data, spend money, publish content, or alter production state. The stronger the side effect, the less acceptable it is to rely on a static shared credential as the trust signal.

This is especially important when the model can act across multiple tools. A shared credential can hide whether the action came from a harmless query, a mistaken chain of calls, or an abuse path that reused the same access token. Runtime review forces the decision point to sit where the risk actually occurs, not where the integration was originally configured.

When access control is the deciding mechanism, the Authorisation Models Guide helps teams distinguish permission design from transport design, and it is useful to think of shared credentials as a weak transport choice that should never replace explicit authorization policy.

Risk and Threat Considerations

Shared credentials create concentration risk, weak attribution, and larger blast radius. If the same secret is reused across users, workflows, or environments, compromise of one path can silently open many others, and incident response becomes slower because defenders cannot reliably tell which actor triggered the action.

Failure mechanism: The model or any party using the shared secret inherits the same effective authority, so privilege escalation, misuse, or token theft can spread across every workflow that trusts that credential. Revocation is also blunt, because disabling the secret can break unrelated access paths at the same time.

Impact: Teams lose actionable accountability, increase the chance of unauthorized tool use, and make it harder to contain incidents without disrupting legitimate operations.

When the access path reaches external APIs, the problem can become visible in the API control plane as well. OWASP Non-Human Identity Top 10 is a useful external reference because it directly addresses secret leakage, overprivilege, and third-party credential risk in non-human access patterns.

Practitioner Guidance

What to prioritise: Identify every shared credential used by model-driven access and classify the actions it can reach. If one secret spans multiple tools, environments, or approval paths, treat it as an immediate hardening target.

What to verify: Confirm that each access path has a named owner, a revocation path, and a runtime control for high-impact actions. If you cannot independently revoke or audit the model path without affecting unrelated users, the design is too coarse.

Common mistake: Teams often focus on whether the model is “allowed” to connect and ignore whether the credential itself proves anything meaningful. It usually does not, especially when the same secret is reused across people, services, or environments.

Practitioner takeaway: The right question is not whether a model can use a shared credential, but whether the credential preserves ownership, limits authority, and supports containment when something goes wrong.

Related resources from NHI Mgmt Group

• How should security teams run access reviews for non-human identities?
• How should security teams govern non-human identities that have persistent access?
• How should security teams govern API keys used for generative AI access?
• How should security teams manage database and infrastructure access without relying on shared secrets or standing credentials?