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Explorer Process Tree Break

SIGMA detection rule by Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), @gott_cyber · NOASSERTION

Detects a command line process that uses explorer.exe to launch arbitrary commands or binaries, which is similar to cmd.exe /c, only it breaks the process tree and makes its parent a new instance of explorer spawning from "svchost"

title: Explorer Process Tree Break
id: 949f1ffb-6e85-4f00-ae1e-c3c5b190d605
status: test
description: |
  Detects a command line process that uses explorer.exe to launch arbitrary commands or binaries,
  which is similar to cmd.exe /c, only it breaks the process tree and makes its parent a new instance of explorer spawning from "svchost"
references:
    - https://twitter.com/CyberRaiju/status/1273597319322058752
    - https://twitter.com/bohops/status/1276357235954909188?s=12
    - https://twitter.com/nas_bench/status/1535322450858233858
    - https://securityboulevard.com/2019/09/deobfuscating-ostap-trickbots-34000-line-javascript-downloader/
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), @gott_cyber
date: 2019-06-29
modified: 2025-10-31
tags:
    - attack.stealth
    - attack.t1036
logsource:
    category: process_creation
    product: windows
detection:
    # Note: See CLSID_SeparateMultipleProcessExplorerHost in the registry for reference
    selection_factory:
        CommandLine|contains: '/factory,{75dff2b7-6936-4c06-a8bb-676a7b00b24b}' # This will catch, the new explorer spawning which indicates a process/tree break. But you won't be able to catch the executing process. For that you need historical data
    selection_root:
        CommandLine|contains: 'explorer.exe'
        CommandLine|contains|windash: ' /root,'
        # There exists almost infinite possibilities to spawn from explorer. The "/root" flag is just an example
        # It's better to have the ability to look at the process tree and look for explorer processes with "weird" flags to be able to catch this technique.
    condition: 1 of selection_*
falsepositives:
    - Unknown
level: medium

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Executable code, not a declarative rule

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