What service helps securely share resources across AWS accounts?

AWS Resource Access Manager (AWS RAM) is specifically designed to facilitate the secure sharing of AWS resources across multiple AWS accounts. It allows you to create resource shares that can include various types of AWS resources such as subnets, transit gateways, and more, enabling collaboration among different AWS accounts while maintaining control over access.

Using AWS RAM, you can grant permissions for resource access without the need to create duplicate resources in each account, which can lead to better management, reduced costs, and improved operational efficiency. Additionally, it supports the principle of least privilege, allowing you to define who can access shared resources and under what conditions.

In contrast, other options do not provide the same functionality for resource sharing across accounts. The AWS Well-Architected Tool focuses on best practices for improving architectures but does not facilitate resource sharing. AWS WAF is a web application firewall that protects applications from web exploits and does not deal with resource sharing, while AWS Directory Service provides directory services for managing users and resources but does not specifically focus on sharing resources across accounts.