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 <code>OpenThread</code>. At this point <code>QueueUserAPC</code> can be used to invoke a function (such as <code>LoadLibrayA</code> 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.
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| PR.PS-05.02 | Mobile code prevention | Mitigates | T1055.004 | Asynchronous Procedure Call |
Comments
Mobile code procedures address specific actions taken to prevent the development, acquisition, and introduction of unacceptable mobile code within organizational systems, including requiring mobile code to be digitally signed by a trusted source.
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| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| SC-18 | Mobile Code | mitigates | T1055.004 | Asynchronous Procedure Call | |
| SI-02 | Flaw Remediation | mitigates | T1055.004 | Asynchronous Procedure Call | |
| SI-03 | Malicious Code Protection | mitigates | T1055.004 | Asynchronous Procedure Call | |
| SI-04 | System Monitoring | mitigates | T1055.004 | Asynchronous Procedure Call | |
| AC-06 | Least Privilege | mitigates | T1055.004 | Asynchronous Procedure Call | |
| SC-07 | Boundary Protection | mitigates | T1055.004 | Asynchronous Procedure Call |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| action.malware.variety.Export data | Export data to another site or system | related-to | T1055.004 | Asynchronous Procedure Call |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| alerts_for_windows_machines | Alerts for Windows Machines | technique_scores | T1055.004 | Asynchronous Procedure Call |
Comments
Injection attacks are specifically cited as a detection focus for Fileless Attack Detection, which is part of this control, with even more specific references to Process Hollowing, executable image injection, and threads started in a dynamically allocated code segment. Detection is periodic at an unknown rate. The following alerts may be generated: "Fileless attack technique detected", "Fileless attack behavior detected", "Fileless attack toolkit detected", "Suspicious SVCHOST process executed".
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| defender_for_app_service | Microsoft Defender for Cloud: Defender for App Service | technique_scores | T1055.004 | Asynchronous Procedure Call |
Comments
Injection attacks are specifically cited as a detection focus for Fileless Attack Detection, which is part of this control, with even more specific references to Process Hollowing, executable image injection, and threads started in a dynamically allocated code segment. Detection is periodic at an unknown rate.
References
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