Salt Typhoon Exchange Web Shell, DLL Sideload, and w3wp Shell Spawn

This rule monitors for suspicious activity related to Microsoft Exchange servers and potential DLL side-loading. It detects the creation of web shell files (.aspx, .ashx, .asmx) in Exchange-related directories, the execution of command shells (cmd, powershell) by the IIS worker process (w3wp.exe) within Exchange, and the side-loading of DLLs by specific signed binaries (dfsvc.exe, rasautou.exe) from non-standard directories.