Event Triggered Execution: Component Object Model Hijacking

Adversaries may establish persistence by executing malicious content triggered by hijacked references to Component Object Model (COM) objects. COM is a system within Windows to enable interaction between software components through the operating system.[1] References to various COM objects are stored in the Registry.

Adversaries can use the COM system to insert malicious code that can be executed in place of legitimate software through hijacking the COM references and relationships as a means for persistence. Hijacking a COM object requires a change in the Registry to replace a reference to a legitimate system component which may cause that component to not work when executed. When that system component is executed through normal system operation the adversary's code will be executed instead.[2] An adversary is likely to hijack objects that are used frequently enough to maintain a consistent level of persistence, but are unlikely to break noticeable functionality within the system as to avoid system instability that could lead to detection.

ID: T1546.015
Sub-technique of:  T1546
Tactics: Privilege Escalation, Persistence
Platforms: Windows
Permissions Required: User
Data Sources: DLL monitoring, Loaded DLLs, Process command-line parameters, Process monitoring, Windows Registry
Contributors: Elastic
Version: 1.0
Created: 16 March 2020
Last Modified: 09 July 2020

Procedure Examples

Name Description
ADVSTORESHELL

Some variants of ADVSTORESHELL achieve persistence by registering the payload as a Shell Icon Overlay handler COM object.[3]

APT28

APT28 has used COM hijacking for persistence by replacing the legitimate MMDeviceEnumerator object with a payload.[4][10]

BBSRAT

BBSRAT has been seen persisting via COM hijacking through replacement of the COM object for MruPidlList {{42aedc87-2188-41fd-b9a3-0c966feabec1}} or Microsoft WBEM New Event Subsystem {{F3130CDB-AA52-4C3A-AB32-85FFC23AF9C1}} depending on the system's CPU architecture.[8]

ComRAT

ComRAT samples have been seen which hijack COM objects for persistence by replacing the path to shell32.dll in registry location HKCU\Software\Classes\CLSID{{42aedc87-2188-41fd-b9a3-0c966feabec1}}\InprocServer32.[6]

JHUHUGIT

JHUHUGIT has used COM hijacking to establish persistence by hijacking a class named MMDeviceEnumerator and also by registering the payload as a Shell Icon Overlay handler COM object ({{3543619C-D563-43f7-95EA-4DA7E1CC396A}}).[4][5]

KONNI

KONNI has modified ComSysApp service to load the malicious DLL payload.[9]

Mosquito

Mosquito uses COM hijacking as a method of persistence.[7]

Mitigations

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.

Detection

There are opportunities to detect COM hijacking by searching for Registry references that have been replaced and through Registry operations (ex: Reg) replacing known binary paths with unknown paths or otherwise malicious content. Even though some third-party applications define user COM objects, the presence of objects within HKEY_CURRENT_USER\Software\Classes\CLSID\ may be anomalous and should be investigated since user objects will be loaded prior to machine objects in HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID.[11] Registry entries for existing COM objects may change infrequently. When an entry with a known good path and binary is replaced or changed to an unusual value to point to an unknown binary in a new location, then it may indicate suspicious behavior and should be investigated.

Likewise, if software DLL loads are collected and analyzed, any unusual DLL load that can be correlated with a COM object Registry modification may indicate COM hijacking has been performed.

References