Suspicious Shell Open Command Registry Modification — Sigma Rule

Rule metadata and linked tags

Author: Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: medium. Source dates: 2026-01-24 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 6779ebe84b1630cc5a497f7723cc697d69ffca282bd24b7d7ba80f1b5025b05c

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: Suspicious Shell Open Command Registry Modification
id: 9e8894c0-0ae0-11ef-9d85-1f2942bec57c
status: experimental
description: |
    Detects modifications to shell open registry keys that point to suspicious locations typically used by malware for persistence.
    Generally, modifications to the `*\shell\open\command` registry key can indicate an attempt to change the default action for opening files,
    and various UAC bypass or persistence techniques involve modifying these keys to execute malicious scripts or binaries.
references:
    - https://www.trendmicro.com/en_us/research/25/f/water-curse.html
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-01-24
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1548.002
    - attack.t1546.001
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|contains: '\shell\open\command\'
        Details|contains:
            - '\$Recycle.Bin\'
            - '\AppData\Local\Temp\'
            - '\Contacts\'
            - '\Music\'
            - '\PerfLogs\'
            - '\Photos\'
            - '\Pictures\'
            - '\Users\Public\'
            - '\Videos\'
            - '\Windows\Temp\'
            - '%AppData%'
            - '%LocalAppData%'
            - '%Temp%'
            - '%tmp%'
    condition: selection
falsepositives:
    - Legitimate software installations or updates that modify the shell open command registry keys to these locations.
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate software installations or updates that modify the shell open command registry keys to these locations.

Source references

• https://www.trendmicro.com/en_us/research/25/f/water-curse.html