Which AWS service would you use to manage user authentication and access control?

AWS Identity and Access Management (IAM) is the service specifically designed for managing user authentication and access control within AWS. With IAM, you can create and manage AWS users and groups, and you can assign permissions to allow or deny access to AWS services and resources. This means that administrators can enforce fine-grained permissions tailored to the needs of individual users or applications, ensuring that the principle of least privilege is maintained.

IAM allows you to manage these permissions through policies, which define what actions are allowed on which resources, giving you comprehensive control over user access. Additionally, IAM supports multifactor authentication (MFA) and can integrate with external identity providers, offering an extra layer of security for managing access to AWS accounts and services.

The other options listed serve different functionalities: AWS CloudTrail is primarily used for logging and monitoring API calls, providing visibility into your AWS account activity; Amazon S3 is a storage service for data; and Amazon DynamoDB is a NoSQL database service. While each of these services plays a crucial role in the AWS ecosystem, they do not handle user authentication and access control like IAM does.