Uncommon File Created by Notepad++ Updater Gup.EXE — Sigma Rule

Rule metadata and linked tags

Author: Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: high. Source dates: 2026-02-03 / 2026-03-16.

{
  "category": "file_event",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 10ddee1298eb1a856ffde770595481ccf885aec9194ea8fe7d6295ddd7e3e453

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Uncommon File Created by Notepad++ Updater Gup.EXE
id: 3b8f4c92-6a51-4d7e-9c3a-8e2d1f5a7b09
status: experimental
description: |
    Detects when the Notepad++ updater (gup.exe) creates files in suspicious or uncommon locations.
    This could indicate potential exploitation of the updater component to deliver unwanted malware or unwarranted files.
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/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-02-03
modified: 2026-03-16
tags:
    - attack.collection
    - attack.credential-access
    - attack.t1195.002
    - attack.initial-access
    - attack.t1557
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\gup.exe'
    filter_main_legit_paths:
        TargetFilename|startswith:
            - 'C:\Program Files\Notepad++\'
            - 'C:\Program Files (x86)\Notepad++\'
    filter_main_temp_update_installer:
        TargetFilename|startswith: 'C:\Users\'
        TargetFilename|contains|all:
            - '\AppData\Local\Temp\'
            - 'npp.'
            - '.Installer.'
            - '.exe'
    filter_main_temp_generic_zip:
        TargetFilename|startswith: 'C:\Users\'
        TargetFilename|contains|all:
            - '\AppData\Local\Temp\'
            - '.zip'
    filter_main_recycle_bin:
        TargetFilename|startswith: 'C:\$Recycle.Bin\S-1-5-21'
    filter_main_plugins:
        - TargetFilename|contains:
              - '\plugins\JsonTools\testfiles\'
              - '\Notepad++\plugins\ComparePlugin\'
        - TargetFilename|contains|all:
              - 'npp.'
              - '.portable.'
              - '\plugins\'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Custom or portable Notepad++ installations in non-standard directories.
    - Legitimate update processes creating temporary files in unexpected locations.
level: high

Original YAML and metadata in JSON

False positives

• Custom or portable Notepad++ installations in non-standard directories.
• Legitimate update processes creating temporary files in unexpected locations.

Source 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/