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Detection rules › Sigma

Uncommon File Created by Notepad++ Updater Gup.EXE

Status
experimental
Severity
high
Log source
product windows, category file_event
Author
Swachchhanda Shrawan Poudel (Nextron Systems)
Source
github.com/SigmaHQ/sigma

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.

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1195.002 Supply Chain Compromise: Compromise Software Supply Chain
Credential AccessT1557 Adversary-in-the-Middle
CollectionT1557 Adversary-in-the-Middle

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

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

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    Image|endswith: '\gup.exe'

Stage 2: not filter_main_*

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\'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
TargetFilenamematch.Installer.
TargetFilenamematch.exe
TargetFilenamematch\AppData\Local\Temp\
TargetFilenamematchnpp.
TargetFilenamestarts_withC:\Users\
TargetFilenamematch.portable.
TargetFilenamematch\plugins\
TargetFilenamematchnpp.
TargetFilenamematch.zip
TargetFilenamematch\AppData\Local\Temp\
TargetFilenamestarts_withC:\Users\
TargetFilenamematch\Notepad++\plugins\ComparePlugin\
TargetFilenamematch\plugins\JsonTools\testfiles\
TargetFilenamestarts_withC:\$Recycle.Bin\S-1-5-21
TargetFilenamestarts_withC:\Program Files (x86)\Notepad++\
TargetFilenamestarts_withC:\Program Files\Notepad++\

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \gup.exe corpus 5 (sigma 5)