Which service can automatically enforce security policies across multiple AWS accounts?

AWS Organizations is the service that can automatically enforce security policies across multiple AWS accounts. This service provides a way to centrally manage and govern your environment as you scale your AWS resources. Through AWS Organizations, you can create multiple accounts under a single master account, which allows for easier billing and resource management.

One of the key features of AWS Organizations is the ability to implement Service Control Policies (SCPs). These policies let administrators define and manage the permissions associated with member accounts, ensuring compliance with security best practices across all accounts in the organization. Therefore, when a security policy is set at the organizational level, it automatically applies to all member accounts, enforcing consistent security standards.

This capability makes AWS Organizations a vital tool for organizations seeking to maintain a strong security posture across their cloud resources, as it simplifies the process of policy enforcement and compliance across multiple accounts.