Avoid user-managed service account keys by using short-lived, automatically issued credentials where possible instead of downloadable long-term key files. Remove existing unused keys, restrict who can create them, and monitor for key creation and use. Where workloads support it, prefer identity federation or attached workload identity rather than static key material.
What counts as avoiding user-managed service account keys
The practical goal is to stop treating downloadable key files as the normal way a workload proves who it is. In Google Cloud, that means preferring short-lived credentials issued from the platform or an external identity provider, and using attached workload identity or federation instead of a long-lived key that a person can copy, store, or reuse. If a key is not needed, the safer state is to remove it.
That shift matters because static keys are durable secrets, while workload identity is an access path that can be bounded, rotated implicitly, and monitored more cleanly. NHIMG’s Google Cloud IAM and Service Accounts Guide and Cloud Workload Identity Guide cover the service-account and federation patterns that replace static key handling in cloud environments.
For teams modernising older deployments, the useful mental model is to separate identity from secret distribution. A service account can still exist, but the question is whether it authenticates with a downloadable secret or with a managed, short-lived credential path. Where possible, the latter should become the default for new workloads and the migration target for old ones.
How to reduce key exposure without breaking workloads
The first control is to prevent unnecessary key creation. Most organisations find that a small number of accounts generate most of the risk because they are easy to reuse across scripts, CI jobs, and ad hoc admin tasks. Limiting who can create keys, and then reviewing whether those keys are actually required, reduces both accidental sprawl and deliberate abuse. Service Account Security Guide is a useful companion for the broader governance and least-privilege patterns behind that decision.
The second control is to migrate workloads to identity-native methods that do not depend on a stored secret file. In Google Cloud, that usually means attached workload identity where the platform can bind the workload to the service account, or federation where an external identity can exchange a trusted assertion for a temporary credential. The objective is not just “more secure keys”, it is removing the key artifact entirely from the normal runtime path.
The third control is operational hygiene. Existing unused keys should be removed, not just noted, because dormant keys are still valid access paths until they are revoked. If a workload still needs a key temporarily, keep the exception narrow, time-bound, and documented so the exception does not become the new default.
What to monitor when keys still exist
If any user-managed keys remain, monitor both creation and use. Key creation is often the earliest sign that a team is bypassing the preferred identity path, while key use can reveal shadow automation, forgotten integrations, or stolen material being exercised outside normal patterns. Alerting on key creation is useful, but it is not enough on its own, because an attacker may only need a single copied file to authenticate quietly.
Workload identity also changes what “good monitoring” looks like. Instead of chasing every secret file, teams should watch for unexpected key material in source control, build logs, tickets, laptops, and shared file stores, then correlate that with service-account activity. The Ultimate Guide to NHIs and the What are Non-Human Identities section are useful for understanding why this lifecycle and visibility problem is larger than one cloud provider.
Google Cloud-specific guidance should be checked in the vendor documentation for exact org policy and workload identity configuration details. The safest operational pattern is to treat every retained key as an exception that must justify its existence, its owner, and its planned removal date.
Risk and Threat Considerations
User-managed service account keys create durable, portable access. If one is copied, leaked, or reused, the attacker may authenticate from anywhere until the key is revoked, which makes the compromise hard to bound in time and location. The risk increases when keys are shared across environments or embedded in automation where many people can touch them.
Failure mechanism: A long-lived key becomes a reusable authentication artifact that bypasses the intended short-lived credential path, so compromise of the file or its storage location can directly translate into unauthorized cloud access.
Impact: The result can be stealthy persistence, unauthorized API calls, privilege misuse, lateral movement through cloud resources, and delayed detection because the activity may look like ordinary service-account authentication.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5, CIS Controls v8, NIST Zero Trust (SP 800-207) and CSA Cloud Controls Matrix set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Covers lifecycle control of credentials and keys used to authenticate workloads. |
| IA-9 — Service Identification and Authentication | Applies when services and workloads authenticate to cloud resources without human sign-in. | |
| AC-6 — Least Privilege | Key reduction and restricted key creation are least-privilege controls for service accounts. | |
| Recommendation — Manage service-account keys as authenticators and revoke unused ones promptly. Prefer managed service authentication paths over downloadable static keys. Limit who can create service-account keys and scope each account minimally. | ||
| CIS Controls v8 | CIS-5 — Account Management | Service-account key removal, restriction, and monitoring are account-management controls. |
| Recommendation — Inventory service accounts, remove stale keys, and monitor key creation. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | User-managed keys are secret material that can leak and enable unauthorized access. |
| NHI-07 — Long-Lived Secrets | The question is fundamentally about avoiding durable key material for service accounts. | |
| NHI-05 — Overprivileged NHI | Key reduction should be paired with minimal permissions on the service account itself. | |
| Recommendation — Replace exposed key files with short-lived credentials and hunt for leaked secrets. Eliminate long-lived service-account keys in favour of ephemeral credentials. Reduce service-account permissions so any credential has minimal blast radius. | ||
| NIST Zero Trust (SP 800-207) | Zero Trust Architecture | Short-lived, strongly bounded workload credentials align with verify-every-access principles. |
| Recommendation — Use identity-based access paths that do not rely on static trust from key possession. | ||
| CSA Cloud Controls Matrix | IAM — Identity & Access Management | Cloud IAM governance directly governs service-account creation, use, and access paths. |
| Recommendation — Apply IAM governance to replace static service-account keys with managed identities. | ||
Practitioner Guidance
What to prioritise: Remove any key that is not required for a live workload first, then identify the remaining workloads that still depend on downloadable keys. That sequence matters because inventory alone does not reduce exposure.
What to verify: Confirm that each surviving service account has an owner, a documented business purpose, and a migration path to short-lived credentials or workload identity. If none exists, treat the key as technical debt with security impact, not as a neutral implementation choice.
Decision rule: If the workload can use federation or attached workload identity, prefer that design; if it cannot, keep the exception narrow and time-limited, and re-evaluate after the dependency is removed. The key is to make static keys the exception, not the architecture.
Practitioner takeaway: The strongest control is not better key storage, it is eliminating the need for user-managed keys wherever the platform can issue short-lived credentials instead.
Related resources from NHI Mgmt Group
- How do you enforce separation of duties for service account and KMS roles in Google Cloud?
- Google Cloud Service Account User Role (roles/iam.serviceAccountUser)
- What problem does ownership attribution solve for service accounts and API keys?
- When do service accounts become a higher risk than ordinary user accounts?