The detection rule monitors for the creation of AWS Elastic Compute Cloud (EC2) network access control lists (ACLs) and their entries, using specified conditions and parameters to identify potential unauthorized or malicious activities. It detects events of network ACL creation invoking AWS's CloudTrail service, by filtering for success outcomes associated with the event actions 'CreateNetworkAcl' and 'CreateNetworkAclEntry'. This rule is critical for maintaining network security, as malicious users can exploit ACLs to persistently access or exfiltrate data from AWS environments. The author suggests using AWS CloudTrail logs to investigate the event further, checking user actions and traffic rules being created to identify potentially risky configurations. Steps for triage include verifying user identity, IP address sourcing, action legitimacy, and correlating other security alerts. Acknowledged false positives stem from routine administrative changes, automated processes, and infrastructure updates, which can be mitigated through documentation and whitelisting approved actions. The rule supports monitoring for compliance with the principle of least privilege and responds through immediate investigations and potential remediation actions to unauthorized ACL modifications.