Potential Proxy Execution Via Explorer.EXE From Shell Process

SIGMA detection rule by Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative · NOASSERTION

Detects the creation of a child "explorer.exe" process from a shell like process such as "cmd.exe" or "powershell.exe". Attackers can use "explorer.exe" for evading defense mechanisms by proxying the execution through the latter. While this is often a legitimate action, this rule can be use to hunt for anomalies. Muddy Waters threat actor was seeing using this technique.

title: Potential Proxy Execution Via Explorer.EXE From Shell Process
id: 9eb271b9-24ae-4cd4-9465-19cfc1047f3e
status: test
description: |
    Detects the creation of a child "explorer.exe" process from a shell like process such as "cmd.exe" or "powershell.exe".
    Attackers can use "explorer.exe" for evading defense mechanisms by proxying the execution through the latter.
    While this is often a legitimate action, this rule can be use to hunt for anomalies.
    Muddy Waters threat actor was seeing using this technique.
references:
    - https://twitter.com/CyberRaiju/status/1273597319322058752
    - https://app.any.run/tasks/9a8fd563-4c54-4d0a-9ad8-1fe08339cbc3/
author: Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative
date: 2020-10-05
modified: 2024-06-21
tags:
    - attack.stealth
    - attack.t1218
    - detection.threat-hunting
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
            - '\pwsh.exe'
        Image|endswith: '\explorer.exe'
        CommandLine|contains: 'explorer.exe'
    condition: selection
falsepositives:
    - Legitimate explorer.exe run from a shell host like "cmd.exe" or "powershell.exe"
level: low

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

522bbbd9-2a06-4532-a4df-2aa5080eecbf

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

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