Winlogon Helper DLL

Status: test
Severity: medium
Log source: category ps_script, product windows
Author: Timur Zinniatullin, oscd.community
Source: github.com/SigmaHQ/sigma

Winlogon.exe is a Windows component responsible for actions at logon/logoff as well as the secure attention sequence (SAS) triggered by Ctrl-Alt-Delete. Registry entries in HKLM\Software[Wow6432Node]Microsoft\Windows NT\CurrentVersion\Winlogon\ and HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ are used to manage additional helper programs and functionalities that support Winlogon. Malicious modifications to these Registry keys may cause Winlogon to load and execute malicious DLLs and/or executables.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1547.004` Boot or Logon Autostart Execution: Winlogon Helper DLL
Privilege Escalation	`T1547.004` Boot or Logon Autostart Execution: Winlogon Helper DLL

Telemetry coverage

Provider	Record / event type
PowerShell	Event ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Winlogon Helper DLL
id: 851c506b-6b7c-4ce2-8802-c703009d03c0
status: test
description: |
    Winlogon.exe is a Windows component responsible for actions at logon/logoff as well as the secure attention sequence (SAS) triggered by Ctrl-Alt-Delete.
    Registry entries in HKLM\Software[Wow6432Node]Microsoft\Windows NT\CurrentVersion\Winlogon\ and HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ are
    used to manage additional helper programs and functionalities that support Winlogon. Malicious modifications to these Registry keys may cause Winlogon to
    load and execute malicious DLLs and/or executables.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1547.004/T1547.004.md
author: Timur Zinniatullin, oscd.community
date: 2019-10-21
modified: 2022-07-07
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1547.004
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains: 'CurrentVersion\Winlogon'
    selection2:
        ScriptBlockText|contains:
            - 'Set-ItemProperty'
            - 'New-Item'
    condition: all of selection*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection*

Stage 1: `selection`

selection:
    ScriptBlockText|contains: 'CurrentVersion\Winlogon'

Stage 2: `selection2`

selection2:
    ScriptBlockText|contains:
        - 'Set-ItemProperty'
        - 'New-Item'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ScriptBlockText`	match	`CurrentVersion\Winlogon` `New-Item` `Set-ItemProperty`	`field:"ScriptBlockText" kind:match`