T1055.004: Asynchronous Procedure Call
| View on MITRE ATT&CK | T1055.004 |
|---|---|
| Tactic(s) | Privilege Escalation, Defense Evasion |
Data from MITRE 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.
© 2024 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.
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MITRE ATT&CK Mitigations
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MITRE ATT&CK Data Components
Process Modification (Process)
Changes made to a process, or its contents, typically to write and/or execute code in the memory of the target process (ex: Sysmon EID 8)OS API Execution (Process)
Operating system function/method calls executed by a processProcess Access (Process)
Opening of a process by another process, typically to read memory of the target process (ex: Sysmon EID 10)Control Validation Tests for this Technique
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