huntrule

Windows Process Creation: OfflineScannerShell.exe mpclient.dll DLL Sideloading Risk

Detects OfflineScannerShell.exe launched with an unexpected current directory that could enable mpclient.dll sideloading.

FreeUnreviewedSigmamediumv1
title: "Windows Process Creation: OfflineScannerShell.exe mpclient.dll DLL Sideloading Risk"
id: e0eb8c83-cffe-40a9-b43b-8410b199ae7f
status: test
description: This rule flags executions of OfflineScannerShell.exe where the process is launched from a non-standard current directory, indicating possible DLL sideloading behavior. OfflineScannerShell.exe is sensitive to loading a DLL named mpclient.dll from the working directory, so attackers can exploit this to run malicious code. The detection relies on process creation telemetry fields including the image path and the process current directory to identify deviations from the expected Offline directory.
references:
  - https://lolbas-project.github.io/lolbas/Binaries/OfflineScannerShell/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_offlinescannershell_mpclient_sideloading.yml
author: frack113, Huntrule Team
date: 2022-03-06
modified: 2023-08-03
tags:
  - attack.stealth
  - attack.t1218
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    - Image|endswith: \OfflineScannerShell.exe
    - OriginalFileName: OfflineScannerShell.exe
  filter_main_legit_dir:
    CurrentDirectory: C:\Program Files\Windows Defender\Offline\
  filter_main_empty:
    CurrentDirectory: ""
  filter_main_null:
    CurrentDirectory: null
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 02b18447-ea83-4b1b-8805-714a8a34546a
    type: derived

What it detects

This rule flags executions of OfflineScannerShell.exe where the process is launched from a non-standard current directory, indicating possible DLL sideloading behavior. OfflineScannerShell.exe is sensitive to loading a DLL named mpclient.dll from the working directory, so attackers can exploit this to run malicious code. The detection relies on process creation telemetry fields including the image path and the process current directory to identify deviations from the expected Offline directory.

Known false positives

  • Unknown

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.