AWS IAM Best Practices

Identity and Access Management forms the foundation of AWS security. Properly configured IAM controls who can access what resources and under what conditions. Poor IAM hygiene creates the attack surface exploited in most cloud breaches.

Fundamental Principles

The root account represents the most powerful and dangerous credential in any AWS environment. Protect the root account by enabling MFA, never creating access keys for it, and configuring alerts for any root account usage. Root should be used only for account-level operations that cannot be performed any other way.

Least privilege requires granting only the permissions necessary to perform required tasks. Start with no permissions and add only what is demonstrably needed. Conduct regular permission reviews to remove accumulated unnecessary access. Leverage AWS Access Analyzer to identify unused permissions and overly permissive policies.

Prefer IAM roles over IAM users for applications and services. EC2 instances should use instance roles for AWS API access. Lambda functions use execution roles. Cross-account access uses assumed roles rather than shared credentials. Roles eliminate the need to manage and rotate long-term credentials.

Policy Best Practices

Write policies following security principles. Use explicit deny statements to prevent specific actions regardless of other permissions. Deny statements in policies always take precedence over allow statements, enabling hard boundaries.

Service Control Policies in AWS Organizations create organization-wide guardrails. SCPs can deny access to regions where your organization should never operate, prevent use of services that violate security requirements, and prevent modification of security controls.

Privileged Access Management

AWS SSO provides centralized access management across multiple accounts with federation to corporate identity providers. Permission boundaries limit the maximum permissions that IAM entities can receive, preventing privilege escalation through delegation. Session policies apply temporary restrictions for specific sessions.

Monitoring and Automation

Enable IAM Access Analyzer to automatically identify resources shared externally and unused permissions. Review credential reports regularly for inactive users and old access keys. Configure CloudWatch alarms for critical IAM actions. Enable GuardDuty for anomaly detection across IAM and other AWS activities.

Automation strengthens IAM security. Infrastructure as Code manages policies consistently. Policy-as-code tools validate policies before deployment. Automated workflows disable inactive credentials without manual intervention.