AWS Systems Manager Session Manager is a service that enables you to securely connect to your EC2 instances without using SSH keys or bastion hosts. You can use Session Manager to access your instances through the AWS Management Console, the AWS CLI, or the AWS SDKs. Session Manager uses IAM policies and roles to control who can access which instances. By attaching the AmazonSSMManagedlnstanceCore IAM policy to an IAM role that is associated with the EC2 instances, you grant the Session Manager service the necessary permissions to perform actions on your instances. You also need to attachanother IAM policy to the developers’ IAM users or roles that allows them to start sessions to the instances. Session Manager uses the AWS Systems Manager Agent (SSM Agent) that is installed by default on Amazon Linux 2 and other supported Linux distributions. Session Manager also encrypts all session data between your client and your instances, and streams session logs to Amazon S3, Amazon CloudWatch Logs, or both for auditing purposes. This solution is the most cost-effective, as it does not require any additional resources or services, such as bastion hosts, VPN connections, or NAT gateways. It also simplifies the security and management of SSH access, as it eliminates the need for SSH keys, port opening, or firewall rules. References:

What is AWS Systems Manager?

Setting up Session Manager

Getting started with Session Manager

Controlling access to Session Manager

Logging Session Manager activity