Suspicious Workstation Locking via Rundll32

 1title: Suspicious Workstation Locking via Rundll32
 2id: 3b5b0213-0460-4e3f-8937-3abf98ff7dcc
 3status: test
 4description: Detects a suspicious call to the user32.dll function that locks the user workstation
 5references:
 6    - https://app.any.run/tasks/2aef9c63-f944-4763-b3ef-81eee209d128/
 7author: frack113
 8date: 2022-06-04
 9modified: 2023-02-09
10tags:
11    - attack.defense-evasion
12logsource:
13    category: process_creation
14    product: windows
15detection:
16    selection_call_img:
17        - Image|endswith: '\rundll32.exe'
18        - OriginalFileName: 'RUNDLL32.EXE'
19    selection_call_parent:
20        ParentImage|endswith: '\cmd.exe'
21    selection_call_cli:
22        CommandLine|contains: 'user32.dll,'
23    selection_function:
24        CommandLine|contains: 'LockWorkStation'
25    condition: all of selection_*
26fields:
27    - Image
28    - ParentImage
29falsepositives:
30    - Scripts or links on the user desktop used to lock the workstation instead of Windows+L or the menu option
31level: medium