Windows: Suspicious Child Process Execution by Notepad++ Updater (gup.exe)

title: "Windows: Suspicious Child Process Execution by Notepad++ Updater (gup.exe)"
id: 1a4c3e70-1155-4cb6-ad94-baf554d10dcd
status: experimental
description: This rule flags process creation events where the Notepad++ updater (gup.exe) spawns a child process associated with command execution or common LOLBin activity. Attackers may abuse updater functionality to run additional payloads by launching script interpreters or signed utility binaries with suspicious command-line content. It relies on Windows process creation telemetry, specifically the parent process image name ending with '\gup.exe', the child process image ending with well-known interpreters, and matching child command-line keywords.
references:
  - https://notepad-plus-plus.org/news/v889-released/
  - https://www.heise.de/en/news/Notepad-updater-installed-malware-11109726.html
  - https://www.rapid7.com/blog/post/tr-chrysalis-backdoor-dive-into-lotus-blossoms-toolkit/
  - https://www.validin.com/blog/exploring_notepad_plus_plus_network_indicators/
  - https://securelist.com/notepad-supply-chain-attack/118708/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_gup_susp_child_process.yml
author: Swachchhanda Shrawan Poudel (Nextron Systems), Huntrule Team
date: 2026-02-03
tags:
  - attack.collection
  - attack.credential-access
  - attack.t1195.002
  - attack.initial-access
  - attack.t1557
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith: \gup.exe
  selection_child_img:
    Image|endswith:
      - \cmd.exe
      - \powershell.exe
      - \pwsh.exe
      - \cscript.exe
      - \wscript.exe
      - \mshta.exe
  selection_child_cli:
    CommandLine|contains:
      - bitsadmin
      - certutil
      - curl
      - finger
      - forfiles
      - regsvr32
      - rundll32
      - wget
  condition: selection_parent and 1 of selection_child_*
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: bb0e87ce-c89f-4857-84fa-095e4483e9cb
    type: derived