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Welcome to CELOS. In this article, you’ll learn how to audit access policies using the IAM Policy Simulator—an essential tool for verifying effective permissions and ensuring no unintended access is granted. Imagine needing to determine the exact permissions available to a user while adjusting policies. The IAM Policy Simulator allows you to check effective permissions resulting from policy modifications, ensuring that the intended policies are applied without any live AWS changes.
The image illustrates the concept of an IAM Policy Simulator, showing a user interacting with a policy document, with AWS tools symbolized in between.

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What is the IAM Policy Simulator?

The IAM Policy Simulator is a testing tool that simulates policy modifications to show you the resulting permissions. When you update a policy that applies to AWS resources, the simulator displays the exact access rights granted—without making any actual live calls to AWS.
The image is a diagram titled "IAM Policy Simulator," showing the relationship between identities (users, groups, roles), permissions (policies), and AWS resources. It illustrates how permissions are applied to identities to access AWS resources.
The IAM Policy Simulator does not perform live AWS requests. It simulates the evaluation of policies, meaning that any changes made in the simulator will not impact your actual AWS configurations.
Important: Service Control Policies (SCPs) with conditions can only simulate allow or deny outcomes without fully mimicking condition restrictions.
The image contains notes about the IAM Policy Simulator, explaining that it doesn't make actual AWS requests, doesn't simulate action responses, and changes made don't affect actual AWS policies.

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Key Features of the IAM Policy Simulator

The simulator evaluates multiple identity-based policies, permission boundaries, and resource-based policy effects. It also analyzes the impact of SCPs during permission evaluation. The tool allows you to test specific services, actions, resources, and context keys (such as IP address or date) to accurately model a variety of conditions.
The image illustrates the capabilities of an IAM Policy Simulator, highlighting six features: testing multiple identity-based policies, permissions boundary simulation, resource-based policy effects, Service Control Policies impact, pre-attachment policy testing, and detailed scenario simulation.

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How to Use the IAM Policy Simulator

Follow these steps to quickly evaluate your IAM policies using the simulator:
  1. Select an IAM Entity: Choose the user, group, or role you want to test.
  2. Configure Simulation Settings: Specify the actions, resources, and conditions (IAM-level conditions, not SCP-level) to be evaluated.
  3. Run the Simulation: Execute the simulation to review the access permissions.
  4. Review and Adjust: Analyze the results and update your policies as needed.
The image outlines four steps to use an IAM Policy Simulator: selecting the IAM entity, configuring simulation settings, running the simulation and reviewing, and adjusting policies.
To use the IAM Policy Simulator, go to policysim.aws.amazon.com and sign in with your AWS console credentials. The interface will display the selected user’s active policies and their corresponding access permissions.
For example, if testing an AWS Batch user, the simulator will display access statuses for specific services. You may notice that actions related to the transit gateway, VPC peering, or elastic IP address are explicitly denied.
The image shows an IAM Policy Simulator interface, displaying a list of Amazon EC2 actions with their permissions status, many of which are denied.

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Benefits of Using the IAM Policy Simulator

Using the IAM Policy Simulator offers multiple advantages:
BenefitDescription
Risk MitigationValidate policy changes without affecting your live environment, reducing potential risks.
Compliance AssuranceEnsure that permissions conform to your organization’s security standards.
Cost EfficiencyAvoid unintended operational costs by testing policies before deployment.
Enhanced Security PostureStrengthen your security by identifying and correcting unintended permissions.
Training and ExperimentationUtilize a safe environment for experimenting and learning about IAM policies.
The image lists five benefits: risk mitigation, compliance assurance, cost efficiency, enhanced security posture, and training and experimentation, alongside an icon of a hand holding a badge.

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Final Thoughts

The IAM Policy Simulator is a powerful tool that enables you to verify the effects of IAM policy changes before applying them to your live AWS environment. It not only enhances your security posture but also serves as an excellent resource for learning and training. Keep these benefits in mind as you fine-tune your IAM policies, ensuring that every change aligns with your organization’s security standards. Thank you for reading. For more detailed information about AWS IAM policies and best practices, consider visiting AWS IAM Documentation.

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