Thread Execution Hijacking
Thread Execution Hijacking [T1055.003]
Information
Name: Thread Execution Hijacking
ID: T1055.003
Technique: T1055
Introduction
Thread Execution Hijacking (T1055.003) is a sub-technique within the MITRE ATT&CK framework under the "Process Injection" technique (T1055). This sub-technique specifically involves adversaries injecting malicious code into existing threads of legitimate processes. By hijacking threads, attackers can execute malicious payloads within the context of trusted processes, thus evading detection and bypassing security controls that monitor for suspicious process creation or unusual activity. Thread Execution Hijacking is commonly leveraged by threat actors to maintain persistence, escalate privileges, and avoid detection by security tools.
Deep Dive Into Technique
Thread Execution Hijacking occurs when an attacker injects malicious code directly into a running thread of a legitimate process. Rather than spawning new processes or threads, the attacker leverages existing threads to execute their payload, minimizing suspicious activity.
Technical details and execution methods include:
Code Injection Methods:
Manipulation of thread context registers (e.g., via
SetThreadContextAPI on Windows).Using Windows APIs such as
SuspendThread,SetThreadContext, andResumeThreadto overwrite the instruction pointer and redirect execution flow.Directly modifying memory regions of the target thread using APIs like
WriteProcessMemory.
Execution Mechanisms:
Suspending an active thread, modifying its context (e.g., instruction pointer), and resuming execution to redirect the thread to attacker-controlled code.
Injecting shellcode or DLL payloads into the memory space of a legitimate process and hijacking a thread to execute this payload.
Leveraging legitimate system processes (e.g., explorer.exe, svchost.exe) to blend malicious actions into normal system behavior.
Advantages for Adversaries:
Avoids creating new processes or threads, reducing the attacker's footprint.
Operates within trusted processes, bypassing application whitelisting and security monitoring.
Enables stealthy persistence and privilege escalation by inheriting privileges from compromised processes.
When this Technique is Usually Used
Adversaries typically employ Thread Execution Hijacking in various attack scenarios and stages:
Initial Access and Execution:
After initial penetration, attackers may inject payloads into legitimate processes to execute malicious code stealthily.
Defense Evasion:
Attackers use this technique to bypass security controls such as antivirus software, endpoint detection and response (EDR), and application whitelisting.
Privilege Escalation:
By hijacking threads within privileged processes, attackers can escalate privileges and gain higher-level access without creating obvious alerts.
Persistence:
Thread hijacking can help maintain persistent access to compromised systems by embedding malicious code within continuously running system processes.
Lateral Movement:
Attackers may use this technique to inject payloads into remote processes on networked systems, facilitating lateral movement and further compromise.
How this Technique is Usually Detected
Detection of Thread Execution Hijacking typically involves monitoring specific behaviors, API calls, and system anomalies. Methods and tools for detection include:
Behavioral Analysis and Endpoint Detection Tools:
Endpoint detection and response (EDR) tools capable of identifying unusual thread activity, suspicious API calls, and memory injections.
Monitoring for API calls such as
SuspendThread,SetThreadContext,ResumeThread, andWriteProcessMemoryused in rapid succession or unusual contexts.
Memory Integrity Monitoring:
Tools that detect unauthorized memory modifications within legitimate processes.
Analyzing unexpected executable memory regions or injected shellcode within trusted processes.
Process and Thread Monitoring:
Observing unusual thread suspensions and context modifications.
Detection of threads executing code from unexpected memory locations or memory pages marked as executable without proper context.
Indicators of Compromise (IoCs):
Suspicious event logs indicating repeated or unusual thread manipulation API calls.
Detection of known malicious shellcode signatures or anomalous executable memory regions.
Unusual network activity initiated from legitimate processes after thread manipulation.
Why it is Important to Detect This Technique
Early detection of Thread Execution Hijacking is critical due to its severe potential impacts on systems and networks, including:
Stealthy Persistence and Long-Term Compromise:
Attackers can maintain hidden persistence by embedding malicious code within legitimate processes, making remediation challenging.
Privilege Escalation and System Control:
Hijacking threads within privileged processes can grant attackers elevated privileges, enabling further exploitation and lateral movement.
Evasion of Security Controls:
By executing malicious payloads within legitimate processes, attackers can evade antivirus, endpoint detection, and application whitelisting measures.
Data Exfiltration and Espionage:
Attackers can leverage compromised threads to access sensitive information, exfiltrate data, or conduct espionage activities undetected.
Operational Disruption and Damage:
Malicious code execution within critical system processes can lead to system instability, crashes, or denial-of-service conditions.
Due to these potential consequences, organizations must prioritize detection and mitigation of this technique to minimize risk and prevent advanced cyber threats.
Examples
Real-world examples and scenarios involving Thread Execution Hijacking include:
Cobalt Strike Framework:
Attackers commonly use Cobalt Strike's Beacon payloads, leveraging thread hijacking techniques to inject shellcode into legitimate processes and maintain persistence.
Cobalt Strike utilizes APIs such as
SuspendThread,SetThreadContext, andResumeThreadto hijack threads and execute payloads stealthily.
Emotet Malware:
Emotet has been observed employing thread hijacking techniques to inject malicious payloads into system processes, allowing it to evade detection and persist within compromised environments.
The malware injects code into trusted processes like explorer.exe or svchost.exe to blend malicious actions with legitimate system activity.
Dridex Banking Trojan:
Dridex uses thread execution hijacking to inject malicious code into browser processes, intercepting banking credentials and sensitive user data without triggering security alerts.
FIN7 Cybercrime Group:
FIN7 has utilized thread hijacking techniques to compromise point-of-sale (POS) systems, injecting malware into running processes to steal payment card information stealthily.
In all these examples, attackers leveraged thread execution hijacking to execute malicious payloads within legitimate processes, evade detection, and achieve their operational goals. These cases highlight the importance of robust detection, monitoring, and defense strategies to identify and mitigate this sophisticated threat technique.
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