The 'CloudTrail Stopped' rule is designed to detect when an AWS CloudTrail trail has been modified to stop logging events. This may indicate potential malicious activity aimed at evading detection. The rule identifies changes made through the AWS API where the action 'StopLogging' is invoked on a specified CloudTrail. It leverages CloudTrail logs, which capture API calls made in the user's AWS account, allowing for the detection of unauthorized changes to logging configurations. The primary focus is on identifying whether the logging functionality has been halted, as this might signify an attempt by an adversary to disable logging in order to conduct nefarious activities on the AWS infrastructure without leaving a trace.