PowerShell Script Retrieval from RTF Resource

This rule detects PowerShell processes attempting to retrieve or execute content from a remote RTF (Rich Text Format) resource. It specifically looks for PowerShell commands like 'Invoke-WebRequest', 'iwr', 'DownloadString', 'Invoke-Expression', or 'iex' that are directed towards a URL ending with '.rtf'. This behavior is often associated with malicious activity where RTF files are used as a delivery mechanism for scripts.