What is AWS IAM?

When you work with AWS, one of the first and most important services you will encounter is AWS Identity and Access Management (IAM). IAM is the service that allows you to securely manage access to your AWS services and resources. It's the backbone of security in your AWS account.

IAM allows you to control who (authentication) can do what (authorization) in your AWS environment. The best part is that IAM is a feature of your AWS account offered at no additional charge.

The Core Components of IAM

IAM is built around four main components:

1. Users: An IAM User is an entity that you create in AWS to represent a person or an application that needs to interact with your AWS resources. A user has a name and credentials (like a password for console access or access keys for programmatic access).

2. Groups: An IAM Group is a collection of IAM users. Groups are a way to manage permissions for multiple users at once. Instead of attaching permissions directly to each user, you can attach permissions to a group. When a user is added to that group, they automatically inherit the group's permissions. This makes managing permissions much easier and more scalable.

3. Policies: An IAM Policy is a JSON document that explicitly defines permissions. A policy states what actions are allowed or denied on which AWS resources. For example, a policy might grant a user permission to read objects from a specific S3 bucket or to launch EC2 instances.

4. Roles: An IAM Role is an identity with permission policies that can be assumed by a trusted entity. A role is similar to a user, but it is not associated with a specific person. Instead, it's intended to be assumed by an application, an AWS service (like EC2), or a user from another AWS account. Roles are the secure way to delegate permissions without having to share long-term credentials like access keys.

The Principle of Least Privilege

The most important concept to follow when working with IAM is the principle of least privilege. This means that you should grant only the minimum permissions that are required for a user or service to perform its task. You should always start with a minimal set of permissions and grant additional permissions only as they are needed.

For example, if an application only needs to read data from an S3 bucket, you should only grant it s3:GetObject permission, not s3:* (which would grant full access, including deletion).

IAM Best Practices

• Don't use your root account user. Your root account user has unrestricted access to everything in your AWS account. You should lock away your root user credentials and create an administrative IAM user for your daily tasks.
• Use groups to manage user permissions. Assigning policies to groups instead of individual users makes your security model easier to manage and reason about.
• Use roles for applications. When an application running on an EC2 instance or in a Lambda function needs to access other AWS resources, you should always use an IAM Role. Never store long-term access keys in your application code or configuration.
• Enable Multi-Factor Authentication (MFA). For all your human users, and especially for your administrative users, you should enable MFA for an extra layer of security.
• Rotate credentials regularly. You should regularly rotate passwords and access keys.

Conclusion

AWS IAM is a fundamental and powerful service that is critical to the security of your cloud environment. By understanding the core concepts of users, groups, roles, and policies, and by adhering to the principle of least privilege, you can build a robust security foundation that allows you to control exactly who can do what in your AWS account. Mastering IAM is the first and most important step to becoming a proficient and responsible AWS user.