Windows Registry: Alert on Changes to \shell\open\command Targeting Common Malware Paths

Alerts on registry_set events modifying \shell\open\command to point to suspicious temp/user-writable locations.

FreeUnreviewedSigmamediumv1

windows-registry-alert-on-changes-to-shell-open-command-targeting-common-malware-9e8894c0

title: "Windows Registry: Alert on Changes to \\shell\\open\\command Targeting Common Malware Paths"
id: 57502685-becd-498f-a858-27d7effb4f5a
status: experimental
description: This rule flags registry modifications to Windows shell open command keys that contain suspicious path indicators often abused for persistence or execution. Attackers may change how files are opened by redirecting the open command to locations under user-writable directories or temporary/per-user areas. The detection relies on registry_set telemetry, matching the TargetObject containing '\shell\open\command\' and Details containing paths such as '$Recycle.Bin', Temp, public user folders, and app-local variables.
references:
  - https://www.trendmicro.com/en_us/research/25/f/water-curse.html
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_set/registry_set_susp_shell_open_keys_modification_patterns.yml
author: Swachchhanda Shrawan Poudel (Nextron Systems), Huntrule Team
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
license: DRL-1.1
related:
  - id: 9e8894c0-0ae0-11ef-9d85-1f2942bec57c
    type: derived

What it detects

This rule flags registry modifications to Windows shell open command keys that contain suspicious path indicators often abused for persistence or execution. Attackers may change how files are opened by redirecting the open command to locations under user-writable directories or temporary/per-user areas. The detection relies on registry_set telemetry, matching the TargetObject containing '\shell\open\command\' and Details containing paths such as '$Recycle.Bin', Temp, public user folders, and app-local variables.

Known false positives

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

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.