In a cloud-first world, securing your AWS environment meticulously goes beyond firewalls and encryption — it also encompasses everything surrounding access — who accesses what, when, and by which means. Cloud security is, fundamentally, about access control. It guarantees that the accurate systems and individuals interact with your resources, and only through validated procedures. Migrating more workloads to AWS leads to increased management complexities for permissions and identities, resulting in robust access control mechanisms becoming critical.

Amazon Web Services (AWS) Identity and Access Management (IAM) is the crux of security in AWS. AWS IAM provides various features including setting up policies which enable you to control, manage, and monitor actions users and groups take within your AWS ecosystem. Implementation of the principle of least privilege, automating access control, and merging with identity management solutions from enterprises are all made possible by IAM. No matter if you are a seasoned cloud engineer or just stepping into the AWS world, learning IAM is the one stop solution for maintaining secure and compliant cloud systems and infrastructures.

In this guide, you’ll learn:

• The main components and concepts of IAM.
• The steps taken in IAM’s operations.
• Special features such as identity federation and permissions boundaries.
• Real-life scenarios and possible mistakes.
• Best practices for IAM in 2025.
• Frequently reviewed questions and recommended professional advice.

After finishing this guide, you will be able to securely define, implement and control access in AWS, safeguarding your workloads while letting your teams work quickly and safely.

What is AWS IAM?

AWS Identity And Access Management (IAM) is a worldwide AWS service that allows the secure administration of AWS resource access. You can manage users, groups and roles as well as permissions that define access levels to specific actions such as EC2, S3, RDS etc.

Why protect AWS resources?

Your cloud infrastructure is built on AWS resources like EC2 instances, S3 buckets and RDS databases. Most of them contain confidential information or host important applications. Improper protection measures can lead to data breaches, outages, or significant monetary losses.

Global scope:

IAM is not bound to a region. Its settings cover your entire AWS account assuring uniform access management to your resources regardless of their location.

Core Components of IAM:

Users:

Definition:

An IAM user is a single person or application that has been granted direct access to AWS. Every user must possess individual credentials (passwords and/or access keys).

Example:

Set up a user ‘John’ with permissions to view S3 resources. Now John will be able to log into the console and have CLI view enabled, but will only be able to view the S3 resources.

Groups:

What are Groups?

They are a set of IAM users. Granting certain permission to a group means all the users under that group automatically get the same predetermined access level.

Why Use Them?

Groups help ease management burdens. For example, a Builders group may have EC2 management permissions. When the permission is granted (or removed) to the group with no additional configuration, the users will automatically have the access without needing to change group settings.

Example:

View S3Bucket is true for the ‘Developers’ group, hence, they are able to start and stop EC2 instances but are not able to delete S3 buckets.

Roles:

Role vs User vs Group:

As has been noted earlier, a role is an identity assigned by AWS along with certain restrictions defined permissions. A role is not linked to any one user permanently. Assigning roles is temporary, which can be done by users, some AWS services, or external identities.

S3 bucket can now be accessed from an EC2 instance without any credentials being hardcoded. The instance takes on a role which AWS takes care of giving critical credentials.

Policies:

Policies Policies are documents like these written in json syntax:

Policies form permissions boundaries which include which actions are permitted or denied, what resources can be acted on, and the conditions under which these can be done.

Managed and Inline Policies.

Managed Policies: These policies can exist on their own, meaning they can be detached or attached to several users, groups, or roles.

Inline Policies: Policies that do grant specific singular permissions within a user, group, or role pouch.

Example:
The below is a JSON policy which gives total control of S3.

{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:*",
"Resource": "*"
}
]
}

Advanced IAM Features.

Identity Federation: Enables users from other identity systems (such as Corporate Directories or Social Logins) to access AWS without creating IAM users. AWS Security Token Service(STS) issues temporary credentials post successful authentication, which mitigates the risk associated with long lived credentials.

IAM Identity Center (AWS SSO):
Enhances and manages access across various AWS accounts and applications from a single point. Connects with identity repositories such as Microsoft Active Directory or SAML 2.0, allowing Single Sign On (SSO) based access for users to all assigned resources.

Permissions Boundaries:

Establish the upper limit of permissions a user or role can have, for example under certain custom policies that are provided in addition to other policies, narrower permissions will be set. Helps in granting a large degree of delegation of scope of permissions management safely in large companies.

Service Linked Roles:

Roles which are tied directly to AWS services so that the services can execute actions using the customer’s identity in a secure manner.

How AWS IAM functions?

IAM maintains security by implementing policies detailing the actions and resources a user or application can manipulate, along with conditions under which these actions can occur.

Policies based on identity:

Bound to users, groups or roles, which specify what resources could be manipulated and what actions can be taken with the input.

Policies based on resources:

Directly bound to resources themselves (Such as S3 buckets policies), allowing definement of who could have access alongside the manner of access.

Authentication:
Checks the identity of a user or application (using password, access keys or federated login).

Authorization:

Verifies the policies provided to see if the action in question is within the limits. Unless allowed by a policy, all actions will, by default, be denied. Policies that deny actions will always take precedence in case of explicit denial.

IAM Best Practices.

• Use the principle of least privilege: Users should be given just the right amount and type of permissions needed for carrying out duties: no more, no less.
• Enable Multi-Factor Authentication (MFA): Require MFA from all users, and especially from privileged or root accounts, for enhanced account security.
• Regularly rotate credentials: Passwords and access keys should be changed periodically to reduce risk in case of credential compromise.
• Use IAM roles for applications and services: AWS credentials should never be embedded within application code. Instead, roles should be assigned to EC2, Lambda, or ECS tasks for secure and temporary access.
• Avoid using the root user for everyday tasks: The root account should be preserved for critical account level actions only.
• Log IAM events with AWS CloudTrail: Evaluate and keep a record of all AWS IAM activity, track suspicious behavior, and ensure compliance for audit purposes.
• Automate audits and reviews: Make use of AWS IAM Access Analyzer, credential reports, and AWS Config for regular auditing at the account level to evaluate access and permissions and ensure compliance.
• “Implement strong password policies” will mean: Implement temperature controls on the password complexity and rotation settings on user accounts.
• “Centralize identity management” means: Use directory service federation and IAM Identity Center to unify access control for multiple accounts.

Real-world AWS IAM Examples.

1. Granting a user read-only S3 access

Step-by-step:

• Go to IAM > Users > Add user in AWS Console.

• Enter username (“John”), select “Programmatic access” and/or “AWS Management Console access.”

• Attach the “AmazonS3ReadOnlyAccess” managed policy.

• Review and create the user.

JSON policy example:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:Get*",
        "s3:List*"
      ],
      "Resource": "*"
    }
  ]
}

2. EC2 instance accessing S3 using a Role

Steps:

• Create an IAM role with the “AmazonS3ReadOnlyAccess” policy.

• Specify “EC2” as the trusted entity.

• Launch or modify your EC2 instance and attach the role.

Policy JSON snippet:
Use the managed policy “AmazonS3ReadOnlyAccess” or the custom policy above.

3. Developers group with limited EC2 access

• Developers can describe, run, stop, start, and terminate EC2 instances, but not manage AMIs or security groups.

Example policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "ec2:DescribeInstances",
        "ec2:RunInstances",
        "ec2:StopInstances",
        "ec2:StartInstances",
        "ec2:TerminateInstances"
      ],
      "Resource": "*"
    }
  ]
}

4. Home and shared directories in S3 for users and groups

• Each user has a home directory in an S3 bucket; developers and managers have shared directories.

Example directory structure:

/amzn-s3-demo-bucket
  /home
    /zhang
    /major
  /share
    /developers
    /managers

Policy for Zhang Wei:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:GetObject", "s3:PutObject", "s3:ListBucket"],
      "Resource": [
        "arn:aws:s3:::amzn-s3-demo-bucket/home/zhang/*",
        "arn:aws:s3:::amzn-s3-demo-bucket/home/zhang/"
      ]
    }
  ]
}

5. Policy for developers to access DynamoDB but deny table deletion

JSON policy snippet:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:PutItem",
        "dynamodb:GetItem",
        "dynamodb:UpdateItem"
      ],
      "Resource": "*"
    },
    {
      "Effect": "Deny",
      "Action": "dynamodb:DeleteTable",
      "Resource": "*"
    }
  ]