Non-human identity: The missing puzzle in zero trust?

Non-human identities (NHI) are everywhere in modern infrastructure, yet they often go unmanaged. This creates blind spots in zero-trust environments. This blog explains how to secure machine credentials using least privilege, automation, and short-lived access, all of which are essential for maintaining a true zero-trust posture.

Key takeaways

• Non-human identities (NHIs), such as service accounts and API keys, are used throughout modern infrastructure but are often left out of zero-trust strategies.
• Ignoring NHIs creates security gaps where credentials are over-permissioned, long-lived, and unaudited.
• Applying zero-trust principles to machine identities means enforcing least privilege, using short-lived credentials, monitoring behavior, and automating management.
• Secrets management platforms help teams integrate these practices into CI/CD pipelines and service-to-service authentication.

If zero trust means never trust, always verify, then why are machines still trusted by default? Why do APIs, cloud services, and automated processes like scripts and CI/CD pipelines get a free pass in environments meant to be airtight? Why do most zero-trust implementations focus on human logins while most activity happens between machines?

Modern infrastructure runs on non-human identities (NHIs). These digital identities authenticate, connect, and automate behind the scenes. They already outnumber human users by a wide margin. Yet, in most organizations, NHIs remain unmanaged, over-permissioned, and invisible, undermining the core principles of zero trust architecture.

This article explores why that’s a serious gap. We’ll cover the security risks, the blind spots, and what it takes to fold NHIs into your zero-trust architecture. We’ll also look at solutions that make integrating NHIs into zero trust both possible and practical.

Why we need NHIs in zero-trust architectures

Zero-trust architecture is a security strategy that assumes no one (inside or outside your network) should be trusted by default. Every user, device, or system must prove who they are and that they can access requested resources every time they try. However, it usually doesn’t account for NHIs.

NHIs handle the majority of system-to-system communication in cloud-native infrastructures. These include the credentials that services, scripts, APIs, and workloads use to talk to each other without human involvement. Ignoring them breaks zero-trust at its foundation; you’re implicitly trusting machines to operate without verifying who they are, what they’re doing, or whether they should even exist.

To make matters worse, NHIs usually have broader, longer-lived access than user accounts. They often persist in the network undetected for months or even years, posing a massive potential entry point for attackers and compliance violations.

A complete zero-trust architecture requires strict access controls for both human and non-human identities. If NHIs aren’t accounted for in your architecture, attackers will find and exploit the gaps.

Why managing NHIs is difficult

Managing non-human identities (NHI) is difficult for a couple of reasons, with some of them highlighted below:

• Usually over-permissioned by default: In practice, NHIs usually get broad or admin-level access to get things working. However, no one comes back to tighten things up, and over time, these identities accumulate way more privileges than they need, which can cause massive exposure if one gets compromised.
• No oversight or expiration: Unlike human users, NHIs don’t get offboarded. For example, an API key created for a quick proof-of-concept can stick around for years while remaining active and still accessing infrastructure resources. Orphaned identities like these become invisible liabilities as they create unmonitored access paths that attackers can exploit.
• Too many, too fast: Modern infrastructure processes frequently require NHIs. Every new microservice, container, or pipeline needs its own identity to access resources or communicate with other services. These identities are usually provisioned automatically at a speed that security teams can’t keep up with.
• Secrets sprawl: Machine credentials can end up hardcoded in source code, left in plaintext config files, pasted into wikis, or logged by accident. Basically, they can be scattered where they don’t belong. This kind of sprawl is almost impossible to audit by hand, and attackers know it. That’s why leaked machine credentials are one of the most common ways breaches start.

How to bring NHIs into zero trust

Bringing non-human identities into a zero-trust architecture mostly means applying the same principles we apply to users, including:

Continuously monitor NHI behavior

Since NHIs can’t use human-oriented methods like single sign-on or multi-factor authentication (MFA), you must compensate by continuously monitoring their behavior. Continuous verification means that even after a machine identity is authenticated, you don’t fully trust it; you keep an eye out for anomalies or misuse.

Additionally, build baselines for what normal behavior looks like for a given service identity, i.e., which other services it talks to, what sensitive data it accesses, and what network paths it usually takes. If that behavior suddenly changes, say, it starts calling sensitive APIs it never touched before or operates from an unexpected location, that could signal a breach. With these behavioral and contextual checks, you can catch misuse of machine credentials in real-time.

Use ephemeral credentials

Another way to secure NHIs is to eliminate long-lived secrets and replace them with ephemeral (short-lived) credentials wherever possible. Stolen credentials are dangerous only as long as they remain valid. For example, rather than using an API key that’s valid indefinitely, use an OAuth or cloud access token that lasts 15 minutes or an hour. If an attacker intercepts that token, it will soon be useless.

Enforce least privilege

Always enforce least privilege access and strict access controls for NHIs. Grant only the permissions needed to perform a task. Just as you wouldn’t give every user domain admin rights, you must avoid giving blanket permissions to service accounts or API tokens.

In practice, this means limiting machine credentials to only what they need to do their job; methods to enforce this include Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC). Furthermore, you should regularly audit and remove unnecessary permissions to avoid privilege creep.

Automate secrets management

With the massive volume of machine identities, manual management is not viable. Leverage automation instead; specifically, use dedicated secrets management tools and automated workflows to handle credential issuance and rotation. For example, instead of hardcoding passwords or API keys in configs, your services should retrieve them from your dedicated secrets management at runtime. This central control also makes it easier to rotate credentials regularly and roll out short-lived secrets.

Automation should also cover the full lifecycle of your machine identities: not just issuance and rotation, but also decommissioning. When a service is retired, its credentials and associated accounts should be revoked and removed automatically to avoid orphaned access.

A practical model for managing NHIs under zero trust

Defining zero-trust principles for NHIs is only step one. The real challenge is integrating those policies into your workflows, and most teams struggle with this because real-world implementation is often messy, manual, and difficult to scale.

Take a simple use case: deploying a microservice that needs access to its config secrets during startup. A zero-trust approach wouldn’t rely on static credentials or broad access. Instead, it would generate a service token scoped specifically to that service and task. The token should be short-lived (just enough to get the service running) and automatically revoked once it’s no longer needed. Ideally, your CI/CD pipeline also handles this entire flow automatically, with no manual steps.

This model reflects core zero-trust principles in action, i.e., least privilege, limited lifetime, and full traceability. The service gets exactly the access it needs for the shortest time possible, and every action is observable. There’s no leftover access to clean up and no blind spots for attackers to exploit.

Secret management tools like Doppler make it easier to build these patterns into your stack. Service tokens in Doppler are scoped and read-only by default, and they can be time-limited to match the short-lived nature of many workloads. You can generate them automatically during deployment and let them expire without any manual cleanup.

In one real-world example, a team used Doppler’s Terraform provider to generate short-lived service tokens for each CI pipeline run. Each token was scoped to a specific config context, had a set expiration time, and was tracked in Git for auditing purposes.

That’s what applying zero trust to NHIs looks like in practice, and when these practices become defaults, you’re no longer hoping your infrastructure is secure; you’re proving it.

Final thoughts

Zero-trust isn’t complete if it ignores machine identities. That’s like locking your front door but leaving the garage wide open. NHIs are everywhere, and they’re too powerful to leave unmanaged.

If you want a real zero-trust setup, humans and machines need to follow the same rules: least privilege, short sessions, and continuous validation. Tools like Doppler make that actually doable without drowning in complexity.

Bringing NHIs into zero-trust doesn’t have to be hard. Try a free Doppler demo and see how to manage machine identities securely without the manual overhead.