Potential MOVEit Transfer CVE-2023-34362 Exploitation - Dynamic Compilation Via Csc.EXE

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About the rule

Rule Type

Standard

Rule Description

Detects the execution of "csc.exe" via "w3wp.exe" process. MOVEit affected hosts execute "csc.exe" via the "w3wp.exe" process to dynamically compile malicious DLL files. MOVEit is affected by a critical vulnerability. Exploited hosts show evidence of dynamically compiling a DLL and writing it under C:\\\\Windows\\\\Microsoft\\.NET\\\\Framework64\\\\v4\\.0\\.30319\\\\Temporary ASP\\.NET Files\\\\root\\\\([a-z0-9]{5,12})\\\\([a-z0-9]{5,12})\\\\App_Web_[a-z0-9]{5,12}\\.dll. Hunting Opportunity Events from IIS dynamically compiling binaries via the csc.exe on behalf of the MOVEit application, especially since May 27th should be investigated.

Severity

Trouble

Rule Requirement

Criteria

Action1: actionname = "Process started" AND PARENTPROCESSNAME endswith "\w3wp.exe" AND PARENTPROCESSCOMMANDLINE contains "moveitdmz pool" AND PROCESSNAME endswith "\csc.exe" select Action1.HOSTNAME,Action1.MESSAGE,Action1.COMMANDLINE,Action1.FILE_NAME,Action1.PROCESSNAME,Action1.USERNAME,Action1.PARENTPROCESSNAME

Detection

Execution Mode

realtime

Log Sources

Windows

Author

@kostastsale