huntrule

Windows File Events: Suspicious Legitimate Apps Dropping Script Files

Detects Windows legitimate/signed executables dropping script files (.ps1, .vbs, .js, etc.) to disk, indicating potential script-based abuse.

FreeUnreviewedSigmahighv1
title: "Windows File Events: Suspicious Legitimate Apps Dropping Script Files"
id: f16a5953-5806-4085-b638-d1dacc0de7a3
status: test
description: This rule flags Windows processes commonly abused in script-based execution that write script file types to disk. It targets cases where a trusted application drops .bat, .js, .ps1, .vbs, .wsf, and other script-like artifacts, which can indicate malware staging or code execution using a legitimate executable. It relies on file creation telemetry that records the initiating process image path and the target filename extensions, with a specific exclusion for the mshta.exe → .hta pairing.
references:
  - https://github.com/Neo23x0/sysmon-config/blob/3f808d9c022c507aae21a9346afba4a59dd533b9/sysmonconfig-export-block.xml#L1326
  - https://dmpdump.github.io/posts/TelegramRat/
  - https://www.virustotal.com/gui/file/a0d5b30578acd1df9139e7a8a4bfc659dc2cf48f4dc0c5804b70890adeb9fa21/behavior
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_susp_legitimate_app_dropping_script.yml
author: frack113, Florian Roth (Nextron Systems), Huntrule Team
date: 2022-08-21
modified: 2026-05-11
tags:
  - attack.stealth
  - attack.t1218
logsource:
  product: windows
  category: file_event
detection:
  selection:
    Image|endswith:
      - \eqnedt32.exe
      - \wordpad.exe
      - \wordview.exe
      - \certutil.exe
      - \certoc.exe
      - \CertReq.exe
      - \Desktopimgdownldr.exe
      - \esentutl.exe
      - \mshta.exe
      - \AcroRd32.exe
      - \RdrCEF.exe
      - \hh.exe
      - \finger.exe
    TargetFilename|endswith:
      - .bat
      - .chm
      - .csproj
      - .hta
      - .js
      - .jse
      - .proj
      - .ps1
      - .py
      - .scf
      - .vbe
      - .vbs
      - .wsf
      - .wsh
  filter_main_mshta:
    Image|endswith: \mshta.exe
    TargetFilename|endswith: .hta
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: high
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_susp_legitimate_app_dropping_script/info.yml
license: DRL-1.1
related:
  - id: 7d604714-e071-49ff-8726-edeb95a70679
    type: derived

What it detects

This rule flags Windows processes commonly abused in script-based execution that write script file types to disk. It targets cases where a trusted application drops .bat, .js, .ps1, .vbs, .wsf, and other script-like artifacts, which can indicate malware staging or code execution using a legitimate executable. It relies on file creation telemetry that records the initiating process image path and the target filename extensions, with a specific exclusion for the mshta.exe → .hta pairing.

Known false positives

  • Unknown

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