Best practices for creating least-privilege AWS IAM policies

AWS Identity and Access Management (IAM) enables organizations to set up permissions policies for users and workloads that need access to cloud services and resources. To properly secure your cloud environment, you need to avoid overly permissive IAM policies, which can lead to security gaps, and overly restrictive ones, which can hinder engineers with AccessDenied errors. Ideally, IAM policies should grant least-privilege permissions (i.e., the minimum level of access required to complete necessary tasks) without blocking workflows. IAM policies define the permissions that govern how IAM entities—users or roles—may access AWS resources. There are several types of IAM policies, including identity-based policies, resource-based policies, Service Control Policies (SCPs), and permissions boundaries. Best practices for defining AWS IAM policies include using wildcards in your Resource and Action elements to specify multiple values, as well as attribute-based access control (ABAC) to create policies that allow a range of actions and access to resources but only to designated requesters. To manage AWS IAM policies at scale, you can choose from two types of policy management—inline policies and managed policies. Inline policies are attached directly to specific identities, enabling you to specify permissions that apply only to that identity. Managed policies exist independent of any AWS identity and can be created and maintained by the organization or provided out-of-the-box by AWS. Tools like Access Analyzer and Datadog Cloud Security Posture Management can help track the security posture of your environment by analyzing IAM policies and highlighting misconfigurations that are commonly found in overly permissive policies.