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Detection rules › Sigma

Potential Proxy Execution Via Explorer.EXE From Shell Process

Status
test
Severity
low
Log source
product windows, category process_creation
Author
Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative
Source
github.com/SigmaHQ/sigma

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.

MITRE ATT&CK coverage

TacticTechniques
StealthT1218 System Binary Proxy Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

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

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ParentImage|endswith:
        - '\cmd.exe'
        - '\powershell.exe'
        - '\pwsh.exe'
    Image|endswith: '\explorer.exe'
    CommandLine|contains: 'explorer.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • explorer.exe corpus 3 (sigma 2, splunk 1)
Imageends_with
  • \explorer.exe corpus 14 (sigma 14)
ParentImageends_with
  • \cmd.exe corpus 20 (sigma 20)
  • \powershell.exe corpus 24 (sigma 24)
  • \pwsh.exe corpus 21 (sigma 21)