Suspicious ScreenSave Change by Reg.exe

Title: Suspicious ScreenSave Change by Reg.exe
Status: test
Description:Adversaries may establish persistence by executing malicious content triggered by user inactivity. Screensavers are programs that execute after a configurable time of user inactivity and consist of Portable Executable (PE) files with a .scr file extension
References:
  -https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1546.002/T1546.002.md
  -https://www.welivesecurity.com/wp-content/uploads/2017/08/eset-gazer.pdf
Author: frack113
Date: 2021-08-19
modified:2022-06-02
Tags:

• -'attack.persistence'
• -'attack.privilege-escalation'
• -'attack.t1546.002'

Logsource:

• category: process_creation
• product: windows

Detection:
  selection_reg:
    Image|endswith: '\reg.exe'
    CommandLine|contains:
      -'HKEY_CURRENT_USER\Control Panel\Desktop'
      -'HKCU\Control Panel\Desktop'

  selection_option_1:
    CommandLine|contains|all:
      -'/v ScreenSaveActive'
      -'/t REG_SZ'
      -'/d 1'
      -'/f'

  selection_option_2:
    CommandLine|contains|all:
      -'/v ScreenSaveTimeout'
      -'/t REG_SZ'
      -'/d '
      -'/f'

  selection_option_3:
    CommandLine|contains|all:
      -'/v ScreenSaverIsSecure'
      -'/t REG_SZ'
      -'/d 0'
      -'/f'

  selection_option_4:
    CommandLine|contains|all:
      -'/v SCRNSAVE.EXE'
      -'/t REG_SZ'
      -'/d '
      -'.scr'
      -'/f'

  condition:selection_reg and 1 of selection_option_*
Falsepositives:
  -GPO
Level: medium