Windows: Clfs.sys Loaded from Suspicious Process Image Paths

Alerts when clfs.sys is loaded by a process running from user/temp/perflogs-style suspicious paths on Windows.

FreeReviewedSigma · Medium · v2

Product: windows
Category: image_load
Author: X__Junior (SigmaHQ), DRL 1.1
Published: 2025-01-20
Updated: 2026-07-31

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1059Command and Scripting Interpreter
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags image loads where clfs.sys is loaded by a process whose image path is located in common suspicious directories (e.g., Perflogs, Public, Temporary Internet, Windows Temp, or user Favorites/Favourites, Contacts, Pictures). Such DLL/driver loading from unusual locations can indicate exploitation or staging activity rather than normal system behavior. It relies on image load telemetry for the loaded module name (clfs.sys) and the loading process image path.

Reporting behind it

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Windows: Clfs.sys Loaded from Suspicious Process Image Paths

Pivot detection · T1059 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-clfs-sys-image-loaded-from-potentially-suspicious-user-or-temp-paths-fb4e2211

title: "Windows: Clfs.sys Loaded from Suspicious Process Image Paths"
id: 0a6de055-0d61-4a43-9423-f4bba73626c7
status: experimental
description: This rule flags image loads where clfs.sys is loaded by a process whose image path is located in common suspicious directories (e.g., Perflogs, Public, Temporary Internet, Windows Temp, or user Favorites/Favourites, Contacts, Pictures). Such DLL/driver loading from unusual locations can indicate exploitation or staging activity rather than normal system behavior. It relies on image load telemetry for the loaded module name (clfs.sys) and the loading process image path.
references:
  - https://ssd-disclosure.com/ssd-advisory-common-log-file-system-clfs-driver-pe/
  - https://x.com/Threatlabz/status/1879956781360976155
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_clfs_load.yml
author: X__Junior, Huntrule Team
date: 2025-01-20
tags:
  - attack.execution
  - attack.t1059
logsource:
  category: image_load
  product: windows
detection:
  selection_dll:
    ImageLoaded|endswith: \clfs.sys
  selection_folders_1:
    Image|contains:
      - :\Perflogs\
      - :\Users\Public\
      - \Temporary Internet
      - \Windows\Temp\
  selection_folders_2:
    - Image|contains|all:
        - :\Users\
        - \Favorites\
    - Image|contains|all:
        - :\Users\
        - \Favourites\
    - Image|contains|all:
        - :\Users\
        - \Contacts\
    - Image|contains|all:
        - :\Users\
        - \Pictures\
  condition: selection_dll and 1 of selection_folders_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: fb4e2211-6d08-426b-8e6f-0d4a161e3b1d
    type: derived

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