A company operates an Amazon EC2 instance that is registered as a target of a...

Network ACLs arestatelessand are evaluated in order based on rule number, with lower rule numbers taking precedence. According to AWS Certified Security – Specialty incident response guidance, network ACLs can be used toimmediately block traffic at the subnet levelwithout restarting instances or modifying their runtime state.

By adding a deny rule with alower priority number (10)that explicitly denies TCP traffic on port 22 from the offending IP address (10.0.1.5), the unauthorized SSH session is immediately interrupted. This approach satisfies the requirement to keep the instance running and to preserve memory for forensic analysis.

Option A violates the requirement because restarting the instance clears memory. Option C would disrupt all legitimate SSH access, not just the unauthorized session. Option D would block all internet access and could cause widespread service disruption.

AWS documentation emphasizes usingnetwork ACL deny rules for rapid, targeted containmentwhen immediate interruption is required without altering instance state.

AWS Certified Security – Specialty Official Study Guide

Amazon VPC Network ACL Documentation

AWS Incident Response Best Practices