SCR File Write Event — Sigma Rule

Rule metadata and linked tags

Author: Christopher Peacock @securepeacock, SCYTHE @scythe_io. Source status: test; severity: medium. Source dates: 2022-04-27 / 2023-08-23.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 7dfcab08c65b02c473687bcc258ead05ae36f172f36e9037d888cebf27eeed93

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: SCR File Write Event
id: c048f047-7e2a-4888-b302-55f509d4a91d
status: test
description: Detects the creation of screensaver files (.scr) outside of system folders. Attackers may execute an application as an ".SCR" file using "rundll32.exe desk.cpl,InstallScreenSaver" for example.
references:
    - https://lolbas-project.github.io/lolbas/Libraries/Desk/
author: 'Christopher Peacock @securepeacock, SCYTHE @scythe_io'
date: 2022-04-27
modified: 2023-08-23
tags:
    - attack.stealth
    - attack.t1218.011
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '.scr'
    filter:
        TargetFilename|contains:
            - ':\$WINDOWS.~BT\NewOS\'
            - ':\Windows\System32\'
            - ':\Windows\SysWOW64\'
            - ':\Windows\WinSxS\'
            - ':\WUDownloadCache\' # Windows Update Download Cache
    condition: selection and not filter
falsepositives:
    - The installation of new screen savers by third party software
level: medium

Original YAML and metadata in JSON

False positives

• The installation of new screen savers by third party software

Source references

• https://lolbas-project.github.io/lolbas/Libraries/Desk/