Windows File Event: Possible Modification of wsl.exe from Installed Location
Alerts on attempts to modify wsl.exe in installed WSL/WindowsApps locations, indicating potential binary replacement for proxy execution.
- Product
- windows
- Category
- file_event
- Author
- Liran Ravich, Swachchhanda Shrawan Poudel (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2026-05-05
- Updated
- 2026-10-03
ATT&CK techniques
Defense EvasionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags file events where wsl.exe is targeted for modification from typical installed paths under Program Files and WindowsApps. Replacing the legitimate wsl.exe binary with a malicious one can lead to proxy execution when a user runs WSL, supporting stealth and defense evasion. It relies on Windows file event telemetry capturing the target filename and associated modifying process image, with exclusions for msiexec and svchost to reduce benign installer/service activity.
Reporting behind it
- cardinalops.comhttps://cardinalops.com/blog/bash-and-switch-hijacking-via-windows-subsystem-for-linux/
- blog.qualys.comhttps://blog.qualys.com/vulnerabilities-threat-research/2022/04/20/implications-of-windows-subsystem-for-linux-for-adversaries-defenders-part-2
- bleepingcomputer.comhttps://www.bleepingcomputer.com/news/security/new-malware-uses-windows-subsystem-for-linux-for-stealthy-attacks/
- thehackernews.comhttps://thehackernews.com/2021/09/new-malware-targets-windows-subsystem.html
- learn.microsoft.comhttps://learn.microsoft.com/en-us/windows/wsl/
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_wsl_binary_modification.yml
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: "Windows File Event: Possible Modification of wsl.exe from Installed Location"
id: 4fb0a153-5d74-4bbf-b483-f349059bbf30
status: experimental
description: This rule flags file events where wsl.exe is targeted for modification from typical installed paths under Program Files and WindowsApps. Replacing the legitimate wsl.exe binary with a malicious one can lead to proxy execution when a user runs WSL, supporting stealth and defense evasion. It relies on Windows file event telemetry capturing the target filename and associated modifying process image, with exclusions for msiexec and svchost to reduce benign installer/service activity.
references:
- https://cardinalops.com/blog/bash-and-switch-hijacking-via-windows-subsystem-for-linux/
- https://blog.qualys.com/vulnerabilities-threat-research/2022/04/20/implications-of-windows-subsystem-for-linux-for-adversaries-defenders-part-2
- https://www.bleepingcomputer.com/news/security/new-malware-uses-windows-subsystem-for-linux-for-stealthy-attacks/
- https://thehackernews.com/2021/09/new-malware-targets-windows-subsystem.html
- https://learn.microsoft.com/en-us/windows/wsl/
- https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_wsl_binary_modification.yml
author: Liran Ravich, Swachchhanda Shrawan Poudel (Nextron Systems), Huntrule Team
date: 2026-05-05
tags:
- attack.stealth
- attack.t1036.005
- attack.t1218
logsource:
category: file_event
product: windows
detection:
selection_wsl_exe:
TargetFilename|endswith: \wsl.exe
selection_wsl_folder:
- TargetFilename|contains:
- :\Program files\wsl\
- :\Program files\WindowsApps\MicrosoftCorporationII.WindowsSubsystemForLinux_
- TargetFilename|contains|all:
- :\Users\
- \AppData\Local\Microsoft\WindowsApps\
filter_main_msiexec:
Image:
- C:\Windows\System32\msiexec.exe
- C:\Windows\SysWOW64\msiexec.exe
filter_main_svchost:
Image: C:\Windows\System32\svchost.exe
TargetFilename|contains: \WindowsApps\
condition: all of selection_* and not 1 of filter_main_*
falsepositives:
- Unlikely
level: medium
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_wsl_binary_modification/info.yml
license: DRL-1.1
related:
- id: 2f400434-01e1-416b-b52c-bb5bfbb9eb78
type: derived