Adversaries may inject malicious code into suspended and hollowed processes in order to evade process-based defenses. Process hollowing is a method of executing arbitrary code in the address space of a separate live process.
Process hollowing is commonly performed by creating a process in a suspended state then unmapping/hollowing its memory, which can then be replaced with malicious code. A victim process can be created with native Windows API calls such as <code>CreateProcess</code>, which includes a flag to suspend the processes primary thread. At this point the process can be unmapped using APIs calls such as <code>ZwUnmapViewOfSection</code> or <code>NtUnmapViewOfSection</code> before being written to, realigned to the injected code, and resumed via <code>VirtualAllocEx</code>, <code>WriteProcessMemory</code>, <code>SetThreadContext</code>, then <code>ResumeThread</code> respectively.(Citation: Leitch Hollowing)(Citation: Endgame Process Injection July 2017)
This is very similar to Thread Local Storage but creates a new process rather than targeting an existing process. This behavior will likely not result in elevated privileges since the injected process was spawned from (and thus inherits the security context) of the injecting process. However, execution via process hollowing 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 |
|---|---|---|---|---|---|
| AC-6 | Least Privilege | Protects | T1055.012 | Process Hollowing | |
| SC-18 | Mobile Code | Protects | T1055.012 | Process Hollowing | |
| SC-7 | Boundary Protection | Protects | T1055.012 | Process Hollowing | |
| SI-2 | Flaw Remediation | Protects | T1055.012 | Process Hollowing | |
| SI-3 | Malicious Code Protection | Protects | T1055.012 | Process Hollowing | |
| SI-4 | System Monitoring | Protects | T1055.012 | Process Hollowing |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| alerts_for_windows_machines | Alerts for Windows Machines | technique_scores | T1055.012 | Process Hollowing |
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".
References
|
| azure_defender_for_app_service | Azure Defender for App Service | technique_scores | T1055.012 | Process Hollowing |
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
|