Uncommon File Created by Notepad++ Updater Gup.EXE

Hunt Hypothesis

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 unwar

Detection Rule

Sigma (Original)

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
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'
    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

KQL (Azure Sentinel)

imFileEvent
| where TargetFilePath endswith "\\gup.exe" and (not(((TargetFileName startswith "C:\\Program Files\\Notepad++\\" or TargetFileName startswith "C:\\Program Files (x86)\\Notepad++\\") or (TargetFileName startswith "C:\\Users\\" and (TargetFileName contains "\\AppData\\Local\\Temp\\" and TargetFileName contains "npp." and TargetFileName contains ".Installer." and TargetFileName contains ".exe")) or (TargetFileName startswith "C:\\Users\\" and (TargetFileName contains "\\AppData\\Local\\Temp\\" and TargetFileName contains ".zip")) or TargetFileName startswith "C:\\$Recycle.Bin\\S-1-5-21")))

Required Data Sources

Sentinel Table	Notes
`imFileEvent`	Ensure this data connector is enabled

False Positive Guidance

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

MITRE ATT&CK Context

Tactic: Collection
Tactic: Credential Access
Tactic: Initial Access
Technique: T1195.002 — Compromise Software Supply Chain

Adversaries may manipulate application software prior to receipt by a final consumer for the purpose of data or system compromise. Supply chain compromise of software can take place in a number of way
Technique: T1557 — Adversary-in-the-Middle

Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as [Network Sniffing](https:/

Validation (Atomic Red Team)

Use these Atomic Red Team tests to validate this detection fires correctly:

T1195.002 — Compromise Software Supply Chain