Potentially Suspicious Child Processes Spawned by ConHost

Status: experimental
Severity: high
Log source: category process_creation, product windows
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.

Known false positives

Legitimate administrative tasks using `conhost.exe` to spawn child processes such as `cmd.exe`, `powershell.exe`, or `regsvr32.exe`.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1202` Indirect Command Execution `T1218` System Binary Proxy Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\cmd.exe` corpus 130 (sigma 130) `\cscript.exe` corpus 72 (sigma 72) `\mshta.exe` corpus 66 (sigma 66) `\powershell.exe` corpus 179 (sigma 178, kusto 1) `\powershell_ise.exe` corpus 41 (sigma 41) `\pwsh.exe` corpus 165 (sigma 164, kusto 1) `\regsvr32.exe` corpus 64 (sigma 64) `\wscript.exe` corpus 74 (sigma 74)	`field:"Image" kind:ends_with`
`OriginalFileName`	eq	`cmd.exe` corpus 81 (sigma 43, elastic 21, splunk 17) `cscript.exe` corpus 32 (sigma 17, elastic 15) `mshta.exe` corpus 40 (elastic 21, sigma 13, splunk 6) `powershell.exe` corpus 138 (sigma 84, splunk 30, elastic 24) `powershell_ise.exe` corpus 51 (splunk 30, sigma 18, elastic 3) `pwsh.dll` corpus 112 (sigma 79, splunk 30, elastic 3) `regsvr32.exe` corpus 37 (sigma 17, elastic 15, splunk 5) `wscript.exe` corpus 38 (elastic 21, sigma 17)	`field:"OriginalFileName" kind:eq`
`ParentImage`	ends_with	`\conhost.exe` corpus 4 (sigma 4)	`field:"ParentImage" kind:ends_with value:"\conhost.exe"`