This detection rule focuses on identifying whether Windows Defender's definition files have been removed on a Windows system, as adversaries often seek to disable security tools to prevent detection of their activities. The rule monitors process creation for the command line used with the Windows Defender command-line utility, MpCmdRun.exe, specifically looking for commands indicating removal of definitions, such as '-RemoveDefinitions -All'. When the specified command line conditions are met, the detection is triggered. Given the high severity level of this rule, it is crucial for organizations to monitor these actions, as they may indicate a breach or misuse of administrative privileges. To effectively use this rule, data sources should include logs from process creation events. Potential false positives could arise from legitimate administrative actions. The specific fields collected during detection include the computer name, user making the change, command line executed, and the parent command line to provide context for the actions taken.