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

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.

Query · sigma

selection:
  ParentImage|endswith: \w3wp.exe
  ParentCommandLine|contains: moveitdmz pool
  Image|endswith: \csc.exe
condition: selection

Known false positives

  • Initial software installation and software updates.
Raw source Potential MOVEit Transfer CVE-2023-34362 Exploitation - Dynamic Compilation Via Csc.EXE · Sigma
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Published by SigmaHQ/sigma ↗, licensed under Detection Rule License 1.1 ↗. Reproduced here unmodified. 
title: Potential MOVEit Transfer CVE-2023-34362 Exploitation - Dynamic Compilation Via Csc.EXE
id: 39ac1fb0-07f1-474b-b97e-c5c0eace0d79
status: test
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.
references:
    - https://www.huntress.com/blog/moveit-transfer-critical-vulnerability-rapid-response
    - https://www.trustedsec.com/blog/critical-vulnerability-in-progress-moveit-transfer-technical-analysis-and-recommendations/
author: '@kostastsale'
date: 2023-06-01
tags:
    - attack.execution
    - attack.t1059
    - cve.2023-34362
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\w3wp.exe'
        ParentCommandLine|contains: 'moveitdmz pool'
        Image|endswith: '\csc.exe'
    condition: selection
falsepositives:
    - Initial software installation and software updates.
level: medium

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