How Access Analyzer Works - AWS Identity and Access Management

How Access Analyzer Works

This topic describes the concepts and terms that are used in Access Analyzer to help you become familiar with how Access Analyzer monitors access to your AWS resources.

AWS IAM Access Analyzer is built on Zelkova, which translates IAM policies into equivalent logical statements, and runs a suite of general-purpose and specialized logical solvers (satisfiability modulo theories) against the problem. Access Analyzer applies Zelkova repeatedly to a policy with increasingly specific queries to characterize classes of behaviors the policy allows, based on the content of the policy. To learn more about satisfiability modulo theories, see Satisfiability Modulo Theories.

Access Analyzer does not examine access logs to determine whether an external entity accessed a resource within your zone of trust. It generates a finding when a resource-based policy allows access to a resource, even if the resource was not accessed by the external entity. Access Analyzer also does not consider the state of any external accounts when making its determination. That is, if it indicates that account 11112222333 can access your S3 bucket, it knows nothing about the state of users, roles, service control policies (SCP), and other relevant configurations in that account. This is for customer privacy – Access Analyzer doesn't consider who owns the other account. It is also for security – if the account is not owned by the Access Analyzer customer, it is still important to know that an external entity could gain access to their resources even if there are currently no principals in the account that could access the resources.

Access Analyzer considers only certain IAM condition keys that external users cannot directly influence, or that are otherwise impactful to authorization.

Access Analyzer does not currently report findings from AWS service principals or internal service accounts. In rare cases where Access Analyzer isn't able to fully determine whether a policy statement grants access to an external entity, it errs on the side of declaring a false positive finding. Access Analyzer is designed to provide a comprehensive view of the resource sharing in your account, and strives to minimize false negatives.