Non-human identity (NHI) API security protects the machine identities that authenticate to APIs without an interactive human login. These identities include service accounts, workloads, CI/CD jobs, API clients, integration principals, bots, certificates, workload federation subjects, and AI agents. They often operate continuously and at machine speed, so excessive privilege or a leaked credential can produce large impact before a human notices.
The security goal is not simply to store API keys safely. It is to know which workload owns each identity, how it proves who it is, which APIs it may call, what data and actions it may reach, how long its credentials live, what normal behavior looks like, and how the identity is disabled when the workload changes or disappears.
What Is a Non-Human Identity?
A non-human identity represents software or infrastructure that needs to authenticate and be authorized. The identity itself is not the secret. It is the logical principal—the workload, service, integration, or agent—and it may prove its identity with different credentials over time.
Service account
A named machine principal used by an application, daemon, job, or platform component.
Workload identity
An identity bound to a runtime such as a VM, pod, cloud service, external OIDC subject, or certificate-bearing workload.
API client
A partner integration, backend service, automation tool, or application identified by a client ID, certificate, key, or token.
AI agent
An autonomous or semi-autonomous software actor that may call tools and APIs using its own identity or delegated user authority.
The key architectural distinction is between identity and credential. A service account may persist for years while the credential used to prove that identity should ideally be short-lived and automatically issued.
Why Non-Human Identities Create API Risk
Machine identities differ from employees in several important ways. They cannot complete MFA prompts, they may run 24/7, they are often created by automation, and ownership can become unclear when teams or applications change.
| Risk | API example | Potential impact |
|---|---|---|
| Long-lived secret | API key embedded in a repository or image | Persistent unauthorized API access |
| Overprivilege | Service token can call admin endpoints it never uses | Large blast radius after compromise |
| Orphaned identity | Deprecated integration remains active | Stealthy persistence and forgotten access path |
| Shared identity | Several workloads use one service account | Poor attribution and hard revocation |
| Human misuse | Developer uses production service credential manually | Bypassed user controls and weak accountability |
| Third-party NHI | Vendor integration token has broad API access | Supply-chain compromise reaches internal APIs |
A Practical NHI Security Model for APIs
Strong NHI security follows the identity across its lifecycle and every API call. Five questions should have explicit answers:
- What is this workload? Use a unique, stable machine identity tied to a specific application or runtime.
- Who owns it? Every NHI needs an accountable team or service owner and a documented business purpose.
- How does it authenticate? Prefer platform/workload identity or short-lived federation over static shared secrets.
- What may it do? Restrict audience, scopes, roles, APIs, environments, tenants, resources, and high-risk actions.
- What is it actually doing? Monitor API endpoints, data, behavior, geography/network context, and deviations from expected use.
Identity systems answer who the workload claims to be. API security still has to determine whether the request is appropriate for that endpoint, object, business flow, and moment.
Choose Credentials That Limit Exposure
| Credential approach | Security profile | Best use |
|---|---|---|
| Static API key | Simple but often long-lived bearer secret; difficult attribution if shared | Legacy/limited integrations with strong rotation and narrow scope |
| Client secret | Better identity semantics but still a stored secret | Confidential clients where stronger alternatives are unavailable |
| mTLS certificate | Cryptographically binds client to key; certificate lifecycle required | Service-to-service and high-assurance partner APIs |
| Short-lived OAuth token | Limited lifetime, audience, and scopes; issuer trust required | Modern API authorization |
| Workload identity federation | Uses trusted runtime identity to obtain short-lived credentials without persistent cloud keys | Cloud, CI/CD, Kubernetes, multicloud, and external workloads |
Google Cloud's current guidance explicitly recommends avoiding service account keys where possible and using workload identity federation or attached service identity instead. The same principle generalizes beyond one cloud: reduce durable bearer secrets and issue short-lived credentials from a trusted workload identity whenever the platform supports it.
Use Workload Federation Carefully
Federation replaces static keys with trust in another identity system. That improves secret management, but the trust mapping itself becomes security-critical.
Google's Workload Identity Federation guidance recommends immutable authoritative attributes, specific audiences, provider/tenant conditions, protection of OIDC metadata/JWKS, and least-privilege mappings. These controls prevent one external subject from being mistaken for another or a token issued for one purpose from being reused elsewhere.
Avoid ambiguous identity mappings
Use stable IDs rather than mutable usernames or repository names where possible. In multi-tenant external identity providers, validate the organization or tenant, not only the common issuer. A correct signature from a shared issuer does not prove the token came from an approved tenant.
Restrict the audience
Tokens should be intended for the exact federation endpoint or API they reach. Audience restrictions reduce confused-deputy risk and make stolen tokens less reusable.
Manage NHI Ownership, Rotation, and Offboarding
OWASP ranks Improper Offboarding as NHI1:2025. The problem is straightforward: applications disappear, people leave, environments are replaced, but service accounts and credentials remain active.
Maintain an inventory that links each NHI to:
- workload/application name and environment;
- owner/team and escalation contact;
- credential mechanism and issuer;
- APIs/resources and privileges;
- last-seen runtime use;
- creation, review, expiration, and offboarding state.
Automate deprovisioning when infrastructure is destroyed or applications are retired. Recertify long-lived identities, rotate any credentials humans could have copied, and alert on dormant identities that suddenly become active.
Monitor Non-Human API Behavior at Runtime
NHIs are predictable compared with humans: a payment worker usually calls a small set of endpoints, a CI job runs from expected infrastructure, and a reporting service has recognizable data-access patterns. That predictability creates strong signals when credentials are abused.
| Runtime signal | Possible risk | Response |
|---|---|---|
| New endpoint/method for established service | Credential theft or privilege expansion | Verify deployment change; block if outside policy |
| Sudden object enumeration | BOLA probing or data collection | Rate-limit and inspect object authorization |
| New tenant/data class | Cross-tenant access or scope misuse | Validate policy and token audience/scope |
| Credential used from human workstation | Human use of NHI or secret theft | Revoke/rotate; require human identity for maintenance |
| Dormant NHI becomes active | Persistence or forgotten integration | Quarantine and revalidate owner/purpose |
| Large response/exfiltration pattern | Compromised service account | Limit extraction; investigate returned sensitive data |
Ammune's API runtime security model can add endpoint, identity, response, data, and behavior context around machine-to-machine traffic.
AI Agents Make NHI Security More Important
AI agents are non-human identities with an additional challenge: their API sequences may be chosen dynamically. An agent can hold or obtain credentials, select tools, chain actions, and operate faster than a person. This makes identity separation and runtime attribution important.
Do not give every agent one shared “AI service” token. Prefer distinct identities by agent/application and preserve delegated user context when the agent acts on behalf of a person. Limit tools and API scopes, bind actions to the current task, and require deterministic policy checks before sensitive operations.
For deeper coverage, see Ammune's guide to API visibility for AI agents.
Non-Human Identity API Security Checklist
- Inventory service accounts, workload identities, API keys, client credentials, certificates, bots, integrations, and agents.
- Assign a unique owner and business purpose to every identity.
- Prefer workload identity/federation and short-lived credentials over static keys.
- Use stable, authoritative identity attributes and explicit audience restrictions.
- Create dedicated identities for distinct applications and environments.
- Apply least privilege to scopes, roles, endpoints, tenants, objects, and actions.
- Keep secrets out of source code, images, logs, tickets, and analytics systems.
- Automate rotation and offboarding; recertify identities periodically.
- Detect human use of machine identities and provide safe human alternatives.
- Baseline API behavior per NHI and alert on new endpoints, data, tenants, volume, or source context.
- Correlate NHI events with deployment, CI/CD, cloud, gateway, and SIEM context.
- Test compromise scenarios: leaked secret, orphaned account, overprivilege, third-party breach, and workload spoofing.
How Ammune Relates to NHI API Security
IAM and workload identity systems should create, authenticate, authorize, rotate, and revoke machine identities. Runtime API security complements those controls by showing what the identity does after authentication.
Ammune can help discover APIs used by services and agents, inspect machine-driven requests and responses, learn normal behavior, identify unusual endpoint or object-access patterns, surface sensitive-data exposure, and provide SIEM-ready evidence tied to the calling identity. This can help distinguish “valid credential” from “expected behavior.”
For broader AI and automation context, see AI-powered API security best practices.
Non-Human Identity Security FAQ
What counts as a non-human identity?
Any software principal that authenticates without an interactive human login can be an NHI: service accounts, cloud workloads, applications, CI/CD jobs, API clients, bots, certificates, integrations, and AI agents.
Are API keys non-human identities?
An API key is usually a credential associated with an application or service identity. The key itself should not be confused with the logical identity and owner it represents.
Why are short-lived credentials safer?
They reduce the useful lifetime of stolen credentials and support automated rotation. When issued from workload identity, they can also remove the need to distribute durable secrets to the application.
What is workload identity federation?
It lets a workload prove its identity through a trusted external environment or identity provider and exchange that assertion for short-lived credentials, instead of storing a long-lived cloud/service-account key.
Should services share one service account?
Usually no. Dedicated identities improve least privilege, attribution, anomaly detection, and revocation. Shared identities make it difficult to determine which workload performed an action and force unrelated services to share permissions.
How do you detect a compromised machine identity?
Look for behavior that departs from the identity's normal API profile: new endpoints, new methods, new tenants, unusual object enumeration, large data responses, unexpected source networks, dormant-to-active transitions, or human workstation use.
How should humans debug systems that use NHIs?
Use named human identities with temporary, audited elevation or controlled impersonation that preserves accountability. Avoid copying production service secrets into developer environments.
Do AI agents need their own identities?
Distinct agent/application identities are strongly useful for least privilege, attribution, revocation, and behavior monitoring. When acting for a user, preserve delegated user/task context rather than collapsing all actions into one shared agent token.
Conclusion
Non-human identity security is now core API security. Replace durable secrets with workload-bound short-lived credentials where possible, create dedicated identities, enforce least privilege, maintain ownership and offboarding, and monitor what each machine identity actually does. The strongest model connects identity lifecycle with API runtime evidence so a valid credential is never treated as proof that every request is safe.