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T1055.004.md

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T1055.004 - Asynchronous Procedure Call

Description from ATT&CK

Adversaries may inject malicious code into processes via the asynchronous procedure call (APC) queue in order to evade process-based defenses as well as possibly elevate privileges. APC injection is a method of executing arbitrary code in the address space of a separate live process.

APC injection is commonly performed by attaching malicious code to the APC Queue (Citation: Microsoft APC) of a process's thread. Queued APC functions are executed when the thread enters an alterable state.(Citation: Microsoft APC) A handle to an existing victim process is first created with native Windows API calls such as OpenThread. At this point QueueUserAPC can be used to invoke a function (such as LoadLibrayA pointing to a malicious DLL).

A variation of APC injection, dubbed "Early Bird injection", involves creating a suspended process in which malicious code can be written and executed before the process' entry point (and potentially subsequent anti-malware hooks) via an APC. (Citation: CyberBit Early Bird Apr 2018) AtomBombing (Citation: ENSIL AtomBombing Oct 2016) is another variation that utilizes APCs to invoke malicious code previously written to the global atom table.(Citation: Microsoft Atom Table)

Running code in the context of another process may allow access to the process's memory, system/network resources, and possibly elevated privileges. Execution via APC injection may also evade detection from security products since the execution is masked under a legitimate process.

Atomic Tests


Atomic Test #1 - Process Injection via C#

Process Injection using C# reference: https://github.com/pwndizzle/c-sharp-memory-injection Excercises Five Techniques

  1. Process injection
  2. ApcInjectionAnyProcess
  3. ApcInjectionNewProcess
  4. IatInjection
  5. ThreadHijack Upon successful execution, cmd.exe will execute T1055.exe, which exercises 5 techniques. Output will be via stdout.

Supported Platforms: Windows

Inputs:

Name Description Type Default Value
exe_binary Output Binary Path PathToAtomicsFolder\T1055.004\bin\T1055.exe

Attack Commands: Run with command_prompt!

#{exe_binary}