The AWS EC2 Gateway Modified rule is designed to detect when an EC2 Network Gateway is modified based on CloudTrail logs. This detection serves as a control measure to identify potential unauthorized changes that could impact network security. The key event monitored by this rule is 'AttachInternetGateway', which indicates an EC2 Internet Gateway has been associated with a VPC (Virtual Private Cloud). The rule leverages specific attributes from the event log, including user identity (assumed role), source IP address, and event time, to substantiate a modification action. It further includes tests to validate consistent behavior, such as confirming that the network gateway modification was indeed executed and that no changes occurred when the expected action was not performed. This rule is part of broader security governance, aligning with the CIS benchmark and MITRE ATT&CK frameworks to mitigate defense evasion tactics.