Identity and Access Management (IAM)

IAM (Identity and Access Management) is the foundation of AWS security, providing fine-grained control over who can access which AWS resources and what actions they can perform. IAM enables you to manage users, groups, roles, and their permissions centrally, ensuring that only authorized entities can access your AWS resources. Understanding IAM is crucial for building secure AWS applications and maintaining compliance with security best practices.

IAM users represent individual people or applications that need access to AWS resources. Each user has unique security credentials and can be assigned specific permissions through policies. Users should be created for each person or application that needs AWS access, avoiding the use of root account credentials for daily operations. Users can have access keys for programmatic access and can be assigned console passwords for web-based access.

IAM groups are collections of users that share common permissions. Instead of assigning policies to individual users, you assign policies to groups and add users to groups. This approach simplifies permission management, especially in organizations with many users. Groups make it easy to grant or revoke permissions for multiple users simultaneously by modifying group policies.

IAM roles are similar to users but are intended to be assumed by trusted entities rather than assigned to specific people. Roles are essential for enabling AWS services to access other services, allowing EC2 instances to access S3, or enabling Lambda functions to access DynamoDB. Roles use temporary security credentials that expire automatically, making them more secure than long-lived access keys. Roles are also used for cross-account access and federated access scenarios.

IAM policies are JSON documents that define permissions. Policies specify what actions are allowed or denied on which resources under what conditions. Policies can be attached to users, groups, or roles. AWS provides managed policies for common use cases, but you can also create custom policies for specific requirements. Understanding policy structure and the policy evaluation logic is essential for implementing proper access control.

The principle of least privilege is fundamental to IAM security. Users, groups, and roles should be granted only the minimum permissions necessary to perform their tasks. This minimizes the potential damage from compromised credentials and reduces the attack surface. Regularly reviewing and auditing IAM permissions ensures that access remains appropriate as roles and responsibilities change.