huntrule

Windows PowerShell Decryption-Like Activity Involving .LNK File Processing

Identifies PowerShell runs that enumerate and process *.lnk content using byte-level reads/writes consistent with decryption staging.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2023-06-30
Updated
2026-07-30
AnalysisDetection
title: Windows PowerShell Decryption-Like Activity Involving .LNK File Processing
id: f6e31262-5239-45aa-aaf3-f9ba46f64818
status: test
description: This rule flags PowerShell executions (powershell.exe or pwsh.exe) whose command lines reference reading .LNK files and performing decryption-like byte handling. It looks for Get-ChildItem/dir enumeration, content retrieval (e.g., Get-Content/ReadAllBytes), and output via WriteAllBytes with properties expansion on *.lnk files. This matters because attackers can use PowerShell to transform embedded or stored data from shortcut files to stage subsequent payloads. Telemetry relies on Windows process creation data including Image/OriginalFileName and the full CommandLine.
references:
  - https://research.checkpoint.com/2023/chinese-threat-actors-targeting-europe-in-smugx-campaign/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_decrypt_pattern.yml
author: X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-06-30
modified: 2023-12-05
tags:
  - attack.execution
logsource:
  product: windows
  category: process_creation
detection:
  selection_img:
    Image|endswith:
      - \powershell.exe
      - \pwsh.exe
    OriginalFileName:
      - PowerShell.EXE
      - pwsh.dll
  selection_cli_dir:
    CommandLine|contains:
      - "Get-ChildItem "
      - "dir "
      - "gci "
      - "ls "
  selection_cli_gc:
    CommandLine|contains:
      - "Get-Content "
      - "gc "
      - "cat "
      - "type "
      - ReadAllBytes
  selection_cli_specific:
    - CommandLine|contains|all:
        - " ^| "
        - \*.lnk
        - -Recurse
        - "-Skip "
    - CommandLine|contains|all:
        - " -ExpandProperty "
        - \*.lnk
        - WriteAllBytes
        - " .length "
  condition: all of selection_*
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: 434c08ba-8406-4d15-8b24-782cb071a691
    type: derived