What is the primary function of a Security Group in AWS?

The primary function of a Security Group in AWS is to act as a virtual firewall to manage inbound and outbound traffic to AWS resources, such as EC2 instances. Security Groups operate at the instance level, which means that they are associated with specific instances rather than at the network level like network ACLs (Access Control Lists).

When you configure a Security Group, you define rules that specify which traffic is allowed to reach your instances based on parameters like IP address, port number, and protocol. This capability allows administrators to control access to resources securely and establish a defense-in-depth mechanism to protect their application environments in the cloud.

Additionally, Security Groups are stateful, which means if you allow an incoming request, the corresponding outgoing response is automatically allowed, irrespective of the outbound rules. This behavior facilitates a simplified management experience over traditional firewall models.

In contrast, choices related to controlling user permissions, storing data, or providing encryption pertain to other AWS services and functionalities that do not directly involve the primary role of Security Groups.