The rule "PowerShell DownloadFile_DownloadString" aims to identify suspicious PowerShell command executions that involve the downloading of files from external sources. Adversaries often utilize such capabilities to pull malicious tools or scripts into compromised environments, generally through command and control channels. This rule specifically looks for the use of the DownloadFile and DownloadString methods of the System.Net.WebClient class within PowerShell. By monitoring for these commands, security teams can detect unauthorized download attempts that could signify a potential compromise or malicious activity. The rule also filters out benign usages of PowerShell, especially those involving Invoke-WebRequest and Invoke-Expression, as these are managed by separate detections. This approach helps minimize false positives while effectively identifying genuine threats related to file transfers from external servers.