AWS Certified Security Specialty SCS-C02 Practice Test 2025 – Your All-in-One Guide to Exam Success!

Utilizing security groups and network ACLs is the most effective way to secure instances located in a public subnet. Security groups act as virtual firewalls for your instances, allowing you to define inbound and outbound rules based on IP protocols, ports, and source/destination IP addresses. This granular control enables you to limit traffic to only what is necessary, thereby reducing the attack surface of your instances.

Network ACLs, on the other hand, provide an additional layer of security at the subnet level. They operate as stateless firewalls that can control traffic in both directions, allowing or denying traffic based on defined rules. By effectively configuring both security groups and network ACLs, you can ensure that only authorized traffic reaches your public instances.

In comparison, other options, while they might enhance security in different contexts, do not directly address how to secure instances specifically within a public subnet. For instance, simply using a VPN does not provide protection for public instances and mainly focuses on creating secure connections for accessing the network. Restricting access strictly to a private subnet may isolate instances, but it doesn't directly apply to securing public instances. Turning off all ports may seem secure, but it would also effectively make the instances inaccessible for legitimate use. Thus, the combination of security