file_event_win_new_src_file.yml

title: SCR File Write Event
id: c048f047-7e2a-4888-b302-55f509d4a91d
status: experimental
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: 2023/02/23
tags:
    - attack.defense_evasion
    - attack.t1218.011
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith: '.scr'
    filter:
        TargetFilename|startswith:
            - 'C:\$WINDOWS.~BT\NewOS\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
            - 'C:\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