t1546-009-appcert-dlls

name	T1546.009_appcert-dlls
description	Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by AppCert DLLs loaded into processes.
category	authorization
version	18.1
author	cyberstrike-official
tags	["mitre-attack","enterprise","t1546.009","privilege-escalation","persistence","windows","sub-technique"]
technique_id	T1546.009
tactic	privilege-escalation
all_tactics	["privilege-escalation","persistence"]
platforms	["Windows"]
mitre_url	https://attack.mitre.org/techniques/T1546/009
tech_stack	["windows"]
cwe_ids	["CWE-269"]
chains_with	["T1546","T1546.001","T1546.002","T1546.003","T1546.004","T1546.005","T1546.006","T1546.007","T1546.008","T1546.010","T1546.011","T1546.012","T1546.013","T1546.014","T1546.015","T1546.016","T1546.017","T1546.018"]
prerequisites	["T1546"]
severity_boost	{"T1546":"Chain with T1546 for deeper attack path","T1546.001":"Chain with T1546.001 for deeper attack path","T1546.002":"Chain with T1546.002 for deeper attack path"}

T1546.009 AppCert DLLs

Sub-technique of: T1546

High-Level Description

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.

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.

Kill Chain Phase

• Privilege Escalation (TA0004)
• Persistence (TA0003)

Platforms: Windows

What to Check

• Identify if AppCert DLLs technique is applicable to target environment
• Check Windows systems for indicators of AppCert DLLs
• Verify mitigations are bypassed or absent (1 known mitigations)
• Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

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 Elevation Required: Yes

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}