AWS Security Groups Guide

AWS Security Groups and Network Access Control Lists (NACLs) are critical components in securing cloud environments, serving as virtual firewalls to control network traffic in Amazon Web Services (AWS). Security Groups operate at the instance level, allowing for stateful control of inbound and outbound traffic, while NACLs work at the subnet level and offer stateless filtering. Both tools are essential for implementing Layer 3 and 4 security measures, with Security Groups allowing only "allow" rules and NACLs permitting both "allow" and "deny" rules. Best practices for managing Security Groups involve limiting port ranges, enabling VPC flow logs, and removing unused groups to reduce misconfiguration risks. The document emphasizes the importance of continuous monitoring and verification of Security Group configurations, recommending Cloud Security Posture Management (CSPM) tools and AWS CloudTrail for tracking changes and maintaining security compliance. Understanding the shared responsibility model is crucial, as cloud security is a joint effort between the provider and the user, with Security Groups being the user's responsibility.