Auditing Sharing with IAM Access Analyzer

It is easy to write a policy that accidentally grants access to the public or to an external account. A single overly broad bucket policy can expose sensitive data.

IAM Access Analyzer continuously checks your resources and tells you which ones are shared outside your zone of trust, before an attacker finds them.

Access Analyzer uses automated reasoning (mathematical logic) to analyze resource policies and identify external access.

• It defines a zone of trust, usually your account or organization.
• Any grant reaching outside that zone becomes a finding.

It is proactive analysis, not log review.

External-access analysis covers many resource-policy services, including:

• S3 buckets, IAM roles (trust policies), and KMS keys.
• Lambda functions, SQS queues, Secrets Manager secrets, and more.

For each, it reports who outside your trust zone can access it.

An external-access finding tells you the resource, the external principal, and the permitted actions.

You then decide whether the access is intended (mark it as archived/expected) or a mistake (fix the policy). Intended findings can be suppressed with archive rules so only real surprises remain.

Access Analyzer also detects unused access: IAM roles and users with permissions or credentials they never use.

• Unused roles, unused access keys, and unused permissions all surface.
• Removing them shrinks your attack surface and enforces least privilege.

Before you deploy a policy, Access Analyzer can validate it against more than a hundred checks.

It flags syntax errors, overly broad grants, and security warnings, and suggests improvements. This catches mistakes at authoring time rather than after exposure.

Access Analyzer can generate a least-privilege policy from CloudTrail history.

It examines what actions an identity actually performed and produces a tailored policy granting only those. This turns a broad starter policy into a tight, evidence-based one.

For pipelines, custom policy checks let you assert rules programmatically.

You can verify that a new policy is no more permissive than an approved baseline, or that it never grants specific sensitive actions. These checks fit into CI/CD to block risky changes before merge.

Set the zone of trust to your entire AWS Organization and run Access Analyzer from a delegated administrator account.

Then any sharing that reaches outside the whole organization is flagged, while internal cross-account sharing is treated as trusted. This scales auditing across all accounts.

A healthy workflow: review new findings regularly, archive expected ones with rules, and remediate the rest by tightening policies.

Integrate findings into Security Hub so they sit alongside other security signals in one console.

Use Access Analyzer whenever the question is "what is exposed outside my account?" or "which permissions are unused?"

It complements CloudTrail (what happened) and Config (current state) by answering who can reach my resources through policy logic.

Choose the right tool.

You learned how IAM Access Analyzer guards against unintended sharing.

• External-access findings show resources reachable outside your trust zone.
• Unused-access findings enforce least privilege.
• It also validates and generates policies and runs organization-wide.