File Download Using Notepad++ GUP Utility

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects execution of the Notepad++ updater (gup) from a process other than Notepad++ to download files.

Known false positives

Other parent processes other than notepad++ using GUP that are not currently identified

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: File Download Using Notepad++ GUP Utility
id: 44143844-0631-49ab-97a0-96387d6b2d7c
status: test
description: Detects execution of the Notepad++ updater (gup) from a process other than Notepad++ to download files.
references:
    - https://twitter.com/nas_bench/status/1535322182863179776
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-06-10
modified: 2023-03-02
tags:
    - attack.command-and-control
    - attack.t1105
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\GUP.exe'
        - OriginalFileName: 'gup.exe'
    selection_cli:
        CommandLine|contains|all:
            - ' -unzipTo '
            - 'http'
    filter:
        ParentImage|endswith: '\notepad++.exe'
    condition: all of selection* and not filter
falsepositives:
    - Other parent processes other than notepad++ using GUP that are not currently identified
level: high

Stages and Predicates

Stage 0: `condition`

all of selection* and not filter

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\GUP.exe'
    - OriginalFileName: 'gup.exe'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains|all:
        - ' -unzipTo '
        - 'http'

Stage 3: `not filter`

filter:
    ParentImage|endswith: '\notepad++.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`ParentImage`	ends_with	`\notepad++.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\notepad++.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-unzipTo` corpus 2 (sigma 1, chronicle 1) `http` corpus 52 (sigma 34, elastic 15, chronicle 2, splunk 1)	`field:"CommandLine" kind:match`
`Image`	ends_with	`\GUP.exe` corpus 5 (sigma 5)	`field:"Image" kind:ends_with value:"\GUP.exe"`
`OriginalFileName`	eq	`gup.exe`	`field:"OriginalFileName" kind:eq value:"gup.exe"`