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Detection rules › Sigma

Potentially Suspicious Child Processes Spawned by ConHost

Status
experimental
Severity
high
Log source
product windows, category process_creation
Author
Swachchhanda Shrawan Poudel (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects suspicious child processes related to Windows Shell utilities spawned by conhost.exe, which could indicate malicious activity using trusted system components.

MITRE ATT&CK coverage

TacticTechniques
StealthT1202 Indirect Command Execution, T1218 System Binary Proxy Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Potentially Suspicious Child Processes Spawned by ConHost
id: dfa03a09-8b92-4d83-8e74-f72839b1c407
related:
    - id: 7dc2dedd-7603-461a-bc13-15803d132355
      type: similar
status: experimental
description: Detects suspicious child processes related to Windows Shell utilities spawned by `conhost.exe`, which could indicate malicious activity using trusted system components.
references:
    - https://tria.ge/241015-l98snsyeje/behavioral2
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-02-05
tags:
    - attack.stealth
    - attack.t1202
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\conhost.exe'
    selection_child:
        - Image|endswith:
              - '\cmd.exe'             # Windows Command Prompt
              - '\cscript.exe'         # Windows Script Host (used for scripting exploits)
              - '\mshta.exe'           # MSHTA (HTML Application Host, often abused)
              - '\powershell_ise.exe'  # PowerShell ISE
              - '\powershell.exe'      # Windows PowerShell
              - '\pwsh.exe'            # PowerShell Core
              - '\regsvr32.exe'        # Windows Registry Server (commonly used for exploits)
              - '\wscript.exe'         # Windows Script Host (for executing scripts)
        - OriginalFileName:
              - 'cmd.exe'
              - 'cscript.exe'
              - 'mshta.exe'
              - 'powershell_ise.exe'
              - 'powershell.exe'
              - 'pwsh.dll'
              - 'regsvr32.exe'
              - 'wscript.exe'
    condition: all of selection_*
falsepositives:
    - Legitimate administrative tasks using `conhost.exe` to spawn child processes such as `cmd.exe`, `powershell.exe`, or `regsvr32.exe`.
level: high

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_parent

selection_parent:
    ParentImage|endswith: '\conhost.exe'

Stage 2: selection_child

selection_child:
    - Image|endswith:
          - '\cmd.exe'
          - '\cscript.exe'
          - '\mshta.exe'
          - '\powershell_ise.exe'
          - '\powershell.exe'
          - '\pwsh.exe'
          - '\regsvr32.exe'
          - '\wscript.exe'
    - OriginalFileName:
          - 'cmd.exe'
          - 'cscript.exe'
          - 'mshta.exe'
          - 'powershell_ise.exe'
          - 'powershell.exe'
          - 'pwsh.dll'
          - 'regsvr32.exe'
          - 'wscript.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
Imageends_with
  • \cmd.exe corpus 130 (sigma 130)
  • \cscript.exe corpus 73 (sigma 73)
  • \mshta.exe corpus 67 (sigma 67)
  • \powershell.exe corpus 182 (sigma 182)
  • \powershell_ise.exe corpus 41 (sigma 41)
  • \pwsh.exe corpus 168 (sigma 168)
  • \regsvr32.exe corpus 65 (sigma 65)
  • \wscript.exe corpus 75 (sigma 75)
OriginalFileNameeq
  • cmd.exe corpus 65 (sigma 43, splunk 17, elastic 5)
  • cscript.exe corpus 19 (sigma 17, elastic 2)
  • mshta.exe corpus 22 (sigma 13, splunk 6, elastic 3)
  • powershell.exe corpus 120 (sigma 84, splunk 30, elastic 6)
  • powershell_ise.exe corpus 51 (splunk 30, sigma 18, elastic 3)
  • pwsh.dll corpus 112 (sigma 79, splunk 30, elastic 3)
  • regsvr32.exe corpus 26 (sigma 17, splunk 6, elastic 3)
  • wscript.exe corpus 20 (sigma 17, elastic 3)
ParentImageends_with
  • \conhost.exe corpus 4 (sigma 4)