Suspicious Shell Open Command Registry Modification

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.

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

• T1546.001Change Default File Association
• T1548.002Bypass User Account Control

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