Detection rules › Sigma
Suspicious Userinit Child Process
Detects a suspicious child process of userinit
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Privilege Escalation | T1055 Process Injection |
| Stealth | T1055 Process Injection |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
title: Suspicious Userinit Child Process
id: b655a06a-31c0-477a-95c2-3726b83d649d
status: test
description: Detects a suspicious child process of userinit
references:
- https://twitter.com/SBousseaden/status/1139811587760562176
author: Florian Roth (Nextron Systems), Samir Bousseaden (idea)
date: 2019-06-17
modified: 2025-10-17
tags:
- attack.privilege-escalation
- attack.stealth
- attack.t1055
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|endswith: '\userinit.exe'
filter_main_netlogon:
CommandLine|contains: '\netlogon\'
filter_main_explorer:
- Image|endswith: '\explorer.exe'
- OriginalFileName: 'explorer.exe'
- CommandLine: 'C:\Windows\Explorer.EXE'
filter_main_null:
Image: null
condition: selection and not 1 of filter_main_*
falsepositives:
- Administrative scripts
level: medium
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_main_*Stage 1: selection
selection:
ParentImage|endswith: '\userinit.exe'
Stage 2: not filter_main_*
filter_main_netlogon:
CommandLine|contains: '\netlogon\'
filter_main_explorer:
- Image|endswith: '\explorer.exe'
- OriginalFileName: 'explorer.exe'
- CommandLine: 'C:\Windows\Explorer.EXE'
filter_main_null:
Image: null
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
CommandLine | eq | C:\Windows\Explorer.EXE |
CommandLine | match | \netlogon\ |
Image | ends_with | \explorer.exe |
Image | is_null | |
OriginalFileName | eq | 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.
| Field | Kind | Values |
|---|---|---|
ParentImage | ends_with |
|