Assembly Loading Via CL_LoadAssembly.ps1 — Sigma Rule

Rule metadata and linked tags

Author: frack113, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-05-21 / 2023-08-17.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 82d77b6398cd06d5bc4e7038bc4f005a54444a83e48b69998ad419abcc47899d

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Assembly Loading Via CL_LoadAssembly.ps1
id: c57872c7-614f-4d7f-a40d-b78c8df2d30d
status: test
description: Detects calls to "LoadAssemblyFromPath" or "LoadAssemblyFromNS" that are part of the "CL_LoadAssembly.ps1" script. This can be abused to load different assemblies and bypass App locker controls.
references:
    - https://bohops.com/2018/01/07/executing-commands-and-bypassing-applocker-with-powershell-diagnostic-scripts/
    - https://lolbas-project.github.io/lolbas/Scripts/CL_LoadAssembly/
author: frack113, Nasreddine Bencherchali (Nextron Systems)
date: 2022-05-21
modified: 2023-08-17
tags:
    - attack.stealth
    - attack.t1216
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # Note: As this function is usually called from within powershell, classical process creation even would not catch it. This will only catch inline calls via "-Command" or "-ScriptBlock" flags for example.
        CommandLine|contains:
            - 'LoadAssemblyFromPath '
            - 'LoadAssemblyFromNS '
    condition: selection
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://bohops.com/2018/01/07/executing-commands-and-bypassing-applocker-with-powershell-diagnostic-scripts/
• https://lolbas-project.github.io/lolbas/Scripts/CL_LoadAssembly/