Detection rules › Sigma
WSL Child Process Anomaly
Detects uncommon or suspicious child processes spawning from a WSL process. This could indicate an attempt to evade parent/child relationship detections or persistence attempts via cron using WSL
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth | T1202 Indirect Command Execution, T1218 System Binary Proxy Execution |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
title: WSL Child Process Anomaly
id: 2267fe65-0681-42ad-9a6d-46553d3f3480
related:
- id: dec44ca7-61ad-493c-bfd7-8819c5faa09b # LOLBIN Rule
type: derived
status: test
description: Detects uncommon or suspicious child processes spawning from a WSL process. This could indicate an attempt to evade parent/child relationship detections or persistence attempts via cron using WSL
references:
- https://lolbas-project.github.io/lolbas/OtherMSBinaries/Wsl/
- https://twitter.com/nas_bench/status/1535431474429808642
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-01-23
modified: 2023-08-15
tags:
- attack.execution
- attack.stealth
- attack.t1218
- attack.t1202
logsource:
category: process_creation
product: windows
detection:
selection_parent:
ParentImage|endswith:
- '\wsl.exe'
- '\wslhost.exe'
selection_children_images:
Image|endswith:
# Add more suspicious/uncommon "lolbin" processes
- '\calc.exe'
- '\cmd.exe'
- '\cscript.exe'
- '\mshta.exe'
- '\powershell.exe'
- '\pwsh.exe'
- '\regsvr32.exe'
- '\rundll32.exe'
- '\wscript.exe'
selection_children_paths:
Image|contains:
- '\AppData\Local\Temp\'
- 'C:\Users\Public\'
- 'C:\Windows\Temp\'
- 'C:\Temp\'
- '\Downloads\'
- '\Desktop\'
condition: selection_parent and 1 of selection_children_*
falsepositives:
- Unknown
level: medium
Stages and Predicates
Stage 0: condition
selection_parent and 1 of selection_children_*Stage 1: selection_parent
selection_parent:
ParentImage|endswith:
- '\wsl.exe'
- '\wslhost.exe'
Stage 2: selection_children_images
selection_children_images:
Image|endswith:
- '\calc.exe'
- '\cmd.exe'
- '\cscript.exe'
- '\mshta.exe'
- '\powershell.exe'
- '\pwsh.exe'
- '\regsvr32.exe'
- '\rundll32.exe'
- '\wscript.exe'
Stage 3: selection_children_paths
selection_children_paths:
Image|contains:
- '\AppData\Local\Temp\'
- 'C:\Users\Public\'
- 'C:\Windows\Temp\'
- 'C:\Temp\'
- '\Downloads\'
- '\Desktop\'
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 |
|---|---|---|
Image | ends_with |
|
Image | match |
|
ParentImage | ends_with |
|