AWS STS issues temporary credentials that expire after a short time, while permanent IAM credentials remain valid until they are rotated or revoked. STS is better suited to short term or delegated access because it reduces standing privilege and supports time limited sessions. Permanent credentials are simpler to issue, but they create more persistent risk if exposed.
Temporary sessions and permanent keys solve different access problems
AWS STS is designed for access that should exist only for a limited window, often because an application, role, or operator needs delegated access without carrying a long-lived secret. Permanent IAM credentials are static access material, so they are easier to reuse but also easier to leak, copy, and keep valid far longer than intended. The practical difference is not just duration, but the blast radius of exposure.
With STS, the credential itself is part of a session and expires automatically. That means you can issue access on demand, bound by time and usually by role assumption or federation. Permanent IAM credentials do not expire on their own, so the security outcome depends on later rotation, revocation, and monitoring discipline. If those controls are weak, a stolen key can remain useful for a long time.
When teams compare the two, they are really choosing between ephemeral authority and durable authority. STS aligns well with just-in-time access, short-lived automation, and delegated work where standing privilege should be minimised. Permanent credentials still appear in legacy integrations and simple scripts, but they concentrate risk because compromise is not naturally self-limiting.
For background on the credential lifecycle and why short-lived secrets are preferred over static ones, see Ultimate Guide to NHIs , Static vs Dynamic Secrets and the broader Ultimate Guide to NHIs. STS also fits the same operational pattern as SPIFFE workload identity specification, which emphasises short-lived, attestable credentials instead of durable secrets.
Risk and Threat Considerations
Permanent IAM credentials are attractive to attackers because they can be reused until someone finds and revokes them, which makes secret theft, code exposure, and forgotten automation especially consequential. STS reduces that exposure window, but it does not remove the need to control who can request sessions, what those sessions can do, and whether session duration is appropriately bounded.
Failure mechanism: Long-lived credentials are copied into code, config, logs, or developer tooling, then persist after the original use case has changed. If the credential is later exposed, the attacker gets durable access instead of a time-boxed session.
Impact: Compromise can become persistent access, broader lateral movement, or repeated misuse of the same key across environments until rotation or revocation closes the path. In AWS environments, that often turns a single leak into a prolonged incident.
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 address the attack and risk surface, while CIS Controls v8, NIST CSF 2.0, NIST Zero Trust (SP 800-207) and NIST SP 800-63 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 — Secret Sprawl and Credential Lifetime | Temporary vs permanent AWS credentials directly concerns secret lifetime and exposure window. |
| NHI-03 — Privilege and Access Scope | STS is used to reduce standing privilege and narrow delegated access scope. | |
| NHI-04 — Lifecycle, Rotation, and Revocation | Permanent IAM credentials require active rotation and revocation to limit persistence. | |
| Recommendation — Prefer short-lived credentials and bound session duration over static AWS keys. Constrain assumed roles to the minimum permissions needed for the session. Rotate and revoke long-lived keys on a defined schedule and after any exposure. | ||
| CIS Controls v8 | 6.3 — Manage and Audit Account Permissions | The question is about access duration and privilege persistence across AWS credentials. |
| 5.4 — Securely Store and Manage Authentication Credentials | Permanent IAM keys are authentication credentials whose storage and handling drive risk. | |
| Recommendation — Inventory privileged credentials and remove unnecessary standing access paths. Store credentials securely and replace long-lived secrets with managed alternatives. | ||
| NIST CSF 2.0 | PR.AC — Access Control | The distinction changes how access is issued, bounded, and revoked. |
| PR.DS — Data Security | Credential exposure is a data-security issue because leaked keys expose protected resources. | |
| Recommendation — Apply access control policies that favour time-limited, least-privilege sessions. Protect credential material and limit where long-lived keys can be stored. | ||
| NIST Zero Trust (SP 800-207) | 3.3 — Least-Privilege Access | STS supports zero-trust style, time-bounded access instead of persistent privilege. |
| Recommendation — Issue access only for the minimum time and scope required for the request. | ||
| NIST SP 800-63 | 4.2 — Authenticator and Session Assurance | STS creates short-lived sessions while permanent IAM keys behave like enduring authenticators. |
| Recommendation — Prefer authenticated sessions with bounded lifetime over enduring static credentials. | ||
Practitioner Guidance
What to prioritise: Use STS for delegated and automated access wherever the workflow allows it, and treat permanent credentials as an exception that needs explicit ownership and a documented rotation path. If a key is tied to production access, the security bar should be higher than for a local development token.
What to verify: Check whether the credential is actually needed to persist beyond a session, whether the role assumption path is working as intended, and whether expiry, rotation, and revocation are tested rather than assumed. A credential that never expires should be treated as an elevated control risk, not a convenience.
Common mistake: Teams often keep permanent IAM keys because they simplify integration, then fail to account for the operational burden of tracking them, rotating them, and proving they were removed everywhere they were copied.
Practitioner takeaway: Choose STS when you want access to end automatically with the task; use permanent credentials only when the business case for persistence is strong enough to justify the extra control overhead.
Related resources from NHI Mgmt Group
- What is the difference between IAM roles and standing AWS user credentials for console access?
- What is the difference between short-lived credentials and permanent API keys for NHI security?
- What is the difference between federated SAML or OIDC access and AWS IAM Identity Center?
- What is the difference between AWS SSO based access and relying on separate IAM users for each account?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 17, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
