Adversaries may inject malicious code into hijacked processes in order to evade process-based defenses as well as possibly elevate privileges. Thread Execution Hijacking is a method of executing arbitrary code in the address space of a separate live process.
Thread Execution Hijacking is commonly performed by suspending an existing process then unmapping/hollowing its memory, which can then be replaced with malicious code or the path to a DLL. A handle to an existing victim process is first created with native Windows API calls such as <code>OpenThread</code>. At this point the process can be suspended then written to, realigned to the injected code, and resumed via <code>SuspendThread </code>, <code>VirtualAllocEx</code>, <code>WriteProcessMemory</code>, <code>SetThreadContext</code>, then <code>ResumeThread</code> respectively.(Citation: Elastic Process Injection July 2017)
This is very similar to Process Hollowing but targets an existing process rather than creating a process in a suspended state.
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 Thread Execution Hijacking 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 |
|---|---|---|---|---|
| AC-06 | Least Privilege | Protects | T1055.003 | Thread Execution Hijacking |
| SC-18 | Mobile Code | Protects | T1055.003 | Thread Execution Hijacking |
| SC-07 | Boundary Protection | Protects | T1055.003 | Thread Execution Hijacking |
| SI-02 | Flaw Remediation | Protects | T1055.003 | Thread Execution Hijacking |
| SI-03 | Malicious Code Protection | Protects | T1055.003 | Thread Execution Hijacking |
| SI-04 | System Monitoring | Protects | T1055.003 | Thread Execution Hijacking |