Windows File Creation: Suspicious LNK Double-Extension Targeted by Document/Image Prefixes

Alerts on Windows-created filenames that end in .lnk while containing hidden-looking double extensions (e.g., .doc. .pdf.)

FreeReviewedSigma · Medium · v2

Product: windows
Category: file_event
Author: Nasreddine Bencherchali (Nextron Systems), frack113 (SigmaHQ), DRL 1.1
Published: 2022-11-07
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1036.007Double File Extension
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows file creation events where the target filename ends with “.lnk” while also containing a second extension pattern such as “.doc.”, “.pdf.”, “.jpg.”, or Office extensions embedded in the name. Double-extension LNK filenames are often used to mislead users by leveraging Windows default file-extension hiding behavior. The detection relies on file event telemetry that includes the created/target filename and process image path so it can exclude common “Recent” locations and selected Office executables.

Reporting behind it

Related detections8 linkedT1036.007 — drag to rearrange

Masqueraded Executable With Double Image Extension

Suspicious Double Extension docx Executable Execution (via process_creation)

Suspicious MSC File with Double Extension (via file_event)

Suspicious MSHTA Execution of Polyglot PDF File Spawned by cmd (via process_creation)

Masquerading Noodlophile Payload Execution via Video File Double Extension (via process_creation)

Suspicious Double Extension PDF Executable via Process Creation

Windows Suspicious Double-Extension Execution via Parent Command Line

Windows File Events: Flag Files With Double Extensions (e.g., .docx.exe)

Windows File Creation: Suspicious LNK Double-Extension Targeted by Document/Image Prefixes

Pivot detection · T1036.007 · 8 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-file-creation-suspicious-lnk-double-extension-filenames-3215aa19

title: "Windows File Creation: Suspicious LNK Double-Extension Targeted by Document/Image Prefixes"
id: 4e0f6aa5-22b5-4a67-9920-33e5c33cd66b
related:
  - id: b4926b47-a9d7-434c-b3a0-adc3fa0bd13e
    type: derived
  - id: 3215aa19-f060-4332-86d5-5602511f3ca8
    type: derived
status: test
description: This rule flags Windows file creation events where the target filename ends with “.lnk” while also containing a second extension pattern such as “.doc.”, “.pdf.”, “.jpg.”, or Office extensions embedded in the name. Double-extension LNK filenames are often used to mislead users by leveraging Windows default file-extension hiding behavior. The detection relies on file event telemetry that includes the created/target filename and process image path so it can exclude common “Recent” locations and selected Office executables.
references:
  - https://www.crowdstrike.com/blog/meet-crowdstrikes-adversary-of-the-month-for-june-mustang-panda/
  - https://www.anomali.com/blog/china-based-apt-mustang-panda-targets-minority-groups-public-and-private-sector-organizations
  - https://www.cybereason.com/blog/research/a-bazar-of-tricks-following-team9s-development-cycles
  - https://twitter.com/malwrhunterteam/status/1235135745611960321
  - https://twitter.com/luc4m/status/1073181154126254080
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_susp_lnk_double_extension.yml
author: Nasreddine Bencherchali (Nextron Systems), frack113, Huntrule Team
date: 2022-11-07
modified: 2023-10-18
tags:
  - attack.stealth
  - attack.t1036.007
logsource:
  category: file_event
  product: windows
detection:
  selection:
    TargetFilename|endswith: .lnk
    TargetFilename|contains:
      - .doc.
      - .docx.
      - .jpg.
      - .pdf.
      - .ppt.
      - .pptx.
      - .xls.
      - .xlsx.
  filter_main_recent:
    TargetFilename|contains: \AppData\Roaming\Microsoft\Windows\Recent\
  filter_optional_office_recent:
    Image|endswith:
      - \excel.exe
      - \powerpnt.exe
      - \winword.exe
    TargetFilename|contains: \AppData\Roaming\Microsoft\Office\Recent\
  filter_optional_office_excel:
    Image|endswith: \excel.exe
    TargetFilename|contains: \AppData\Roaming\Microsoft\Excel
  filter_optional_office_powerpoint:
    Image|endswith: \powerpnt.exe
    TargetFilename|contains: \AppData\Roaming\Microsoft\PowerPoint
  filter_optional_office_word:
    Image|endswith: \winword.exe
    TargetFilename|contains: \AppData\Roaming\Microsoft\Word
  condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
  - Some tuning is required for other general purpose directories of third party apps
level: medium
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_susp_lnk_double_extension/info.yml
license: DRL-1.1

Convert

This rule as a query you can run. Uses no unlock credit.

SplunkSPL