T1055.004: Asynchronous Procedure Call
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 [1] of a process's thread. Queued APC functions are executed when the thread enters an alterable state.[1] 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. [2] AtomBombing [3] is another variation that utilizes APCs to invoke malicious code previously written to the global atom table.[4]
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.
Security context for executives and security teams
T1055.004: Asynchronous Procedure Call describes 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 h...
Executive priority
T1055.004: Asynchronous Procedure Call is an official MITRE ATT&CK technique. Glexia treats it as defensive behavior context for prioritizing monitoring, control validation, and response planning without using the object by itself as an attribution claim.
Technical view
Security teams should validate T1055.004: Asynchronous Procedure Call by reviewing the official ATT&CK relationships, mapped tactics (stealth, privilege-escalation), supported platforms (Windows), and available local telemetry before making detection or mitigation decisions.
Likely telemetry
- Official ATT&CK relationships and object metadata
- Identity, privilege, and authentication events
- Network, endpoint, and security-tool telemetry
Detection direction
- Validate whether T1055.004: Asynchronous Procedure Call appears in your detection coverage and tabletop scenarios.
- Use the object to align executive risk language with SOC, incident response, and detection engineering work.
- Do not treat ATT&CK relationship context as attribution without corroborating evidence.
Mitigation priorities
- Map the object to existing controls and identify missing telemetry or response ownership.
- Prioritize mitigations that reduce exposure on the listed platforms and tactics.
- Review adjacent ATT&CK relationships before changing policy, detections, or reporting language.
Additional notes and limits
Baseline Glexia take generated from the official MITRE ATT&CK STIX object, source hash, tactics, platforms, and detection fields. It is safe to replace with a richer model-generated take for the same source hash later.
This baseline take is source-grounded and schema-validated, but it does not include environment-specific telemetry, incident evidence, or threat-intelligence corroboration.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Asynchronous Procedure Call
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 [1] of a process's thread. Queued APC functions are executed when the thread enters an alterable state.[1] 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. [2] AtomBombing [3] is another variation that utilizes APCs to invoke malicious code previously written to the global atom table.[4]
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.
How security teams should use this page
Treat this object as behavior context, not an attribution claim. Validate the related groups, software, data sources, and mitigations against official ATT&CK relationships and your own telemetry before making control-coverage decisions.
Related techniques
This mirrors the MITRE pattern of making group, software, campaign, and technique relationships scannable. Relationship notes come from mirrored ATT&CK relationship text when available.
| Domain | ID | Name | Relationship / procedure |
|---|---|---|---|
| Enterprise | T1055 | Process Injection | This object subtechnique of Process Injection. |
Groups, software, and campaigns
G0061: FIN8
FIN8 is a financially motivated threat group that has been active since at least January 2016, and known for targeting organizations in the hospitality, retail, entertainment, insurance, technology, chemical, and financial sectors. In June 2021, security researchers detected FIN8 switching from targeting point-of-sale (POS) devices to distributing a number of ransomware variants.[1][2][3][4]
S1039: Bumblebee
Bumblebee is a custom loader written in C++ that has been used by multiple threat actors, including possible initial access brokers, to download and execute additional payloads since at least March 2022. Bumblebee has been linked to ransomware operations including Conti, Quantum, and Mountlocker and derived its name from the appearance of "bumblebee" in the user-agent.[1][2][3]
S1085: Sardonic
S9018: HeartCrypt
HeartCrypt is a packer-as-a-service (PaaS) used to protect malware that has been available since at least 2024. HeartCrypt has been used to pack a variety of malware including Lumma Stealer, Remcos, and Rhadamanthys. In the HeartCrypt PaaS model, customers submit malware via private messaging services and it is then packed and returned by the operator as a new binary.[1]
S1081: BADHATCH
S0260: InvisiMole
InvisiMole is a modular spyware program that has been used by the InvisiMole Group since at least 2013. InvisiMole has two backdoor modules called RC2FM and RC2CL that are used to perform post-exploitation activities. It has been discovered on compromised victims in the Ukraine and Russia. Gamaredon Group infrastructure has been used to download and execute InvisiMole against a small number of victims.[1][2]
S0483: IcedID
S1018: Saint Bot
Saint Bot is a .NET downloader that has been used by Saint Bear since at least March 2021.[1][2]
S0438: Attor
S1207: XLoader
S0484: Carberp
S0517: Pillowmint
Pillowmint is a point-of-sale malware used by FIN7 designed to capture credit card information.[1]
S0199: TURNEDUP
TURNEDUP is a non-public backdoor. It has been dropped by APT33's StoneDrill malware. [1] [2]
All related ATT&CK context
Mitigation direction
Object version and sync metadata
The fields below describe the current mirrored snapshot. When Glexia retains multiple ATT&CK source imports, you can open the table to compare the same object across releases (hashes and MITRE timestamps). For MITRE’s own release notes and roadmap, see ATT&CK resources — Updates.
Imported snapshots across ATT&CK releases(2)
| Release | Bundle imported | Object version | Modified | Status | Raw hash |
|---|---|---|---|---|---|
| 19.2 | 2.0 | Current bundle | 281bc96a4612… | ||
| 19.1 | 2.0 | Older bundle | 281bc96a4612… |
Mirrored ATT&CK source object
The raw object is retained through the mirrored ATT&CK source bundle and object hash. The raw endpoint returns the exact object from the mirrored bundle when available.
External references and citations
MITRE external references are preserved separately from Glexia analysis so citations remain traceable to their original source records.
- [1]Microsoft APC
Microsoft. (n.d.). Asynchronous Procedure Calls. Retrieved December 8, 2017.
Open source URL - [2]CyberBit Early Bird Apr 2018
Gavriel, H. & Erbesfeld, B. (2018, April 11). New ‘Early Bird’ Code Injection Technique Discovered. Retrieved May 24, 2018.
Open source URL - [3]ENSIL AtomBombing Oct 2016
Liberman, T. (2016, October 27). ATOMBOMBING: BRAND NEW CODE INJECTION FOR WINDOWS. Retrieved December 8, 2017.
Open source URL - [4]Microsoft Atom Table
Microsoft. (n.d.). About Atom Tables. Retrieved December 8, 2017.
Open source URL - [5]mitre-attackT1055.004Open source URL
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