ScreenSaver Registry Key Set — Sigma Rule

Rule metadata and linked tags

Author: Jose Luis Sanchez Martinez (@Joseliyo_Jstnk). Source status: test; severity: medium. Source dates: 2022-05-04 / 2023-08-17.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 90da4a70d30db0f6daa5b3a21e53ad0ed9ab10ac1c9a27d8094c6486ee00dbc1

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: ScreenSaver Registry Key Set
id: 40b6e656-4e11-4c0c-8772-c1cc6dae34ce
status: test
description: Detects registry key established after masqueraded .scr file execution using Rundll32 through desk.cpl
references:
    - https://twitter.com/VakninHai/status/1517027824984547329
    - https://twitter.com/pabraeken/status/998627081360695297
    - https://jstnk9.github.io/jstnk9/research/InstallScreenSaver-SCR-files
author: Jose Luis Sanchez Martinez (@Joseliyo_Jstnk)
date: 2022-05-04
modified: 2023-08-17
tags:
    - attack.stealth
    - attack.t1218.011
logsource:
    product: windows
    category: registry_set
detection:
    selection:
        Image|endswith: '\rundll32.exe'
    registry:
        TargetObject|contains: '\Control Panel\Desktop\SCRNSAVE.EXE'
        Details|endswith: '.scr'
    filter:
        Details|contains:
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
    condition: selection and registry and not filter
falsepositives:
    - Legitimate use of screen saver
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate use of screen saver

Source references

• https://twitter.com/VakninHai/status/1517027824984547329
• https://twitter.com/pabraeken/status/998627081360695297
• https://jstnk9.github.io/jstnk9/research/InstallScreenSaver-SCR-files