Netsh Helper DLL
Netsh Helper DLL [T1546.007]
Last updated
Netsh Helper DLL [T1546.007]
Last updated
Name: Netsh Helper DLL
ID: T1546.007
Tactics: ,
Technique:
Netsh Helper DLL () refers to a persistence technique within the MITRE ATT&CK framework, categorized under the broader technique "Event Triggered Execution." Adversaries leverage Netsh (Network Shell), a Windows command-line scripting utility, to load malicious DLL files. These DLLs are registered as Netsh helper DLLs, enabling attackers to execute arbitrary code persistently each time the Netsh utility is executed, thereby maintaining long-term access to compromised systems.
Netsh is a legitimate Windows utility designed to configure and display the status of network components. It supports helper DLLs, which extend its functionality by adding custom commands. Attackers exploit this extensibility to achieve persistence and stealthy execution of malicious payloads.
Technical details include:
DLL Registration: Attackers register malicious DLLs as Netsh helper DLLs through modifications in the Windows Registry, typically under:
or
Each helper DLL is registered under a subkey specifying the DLL path and associated commands.
Execution Mechanism: Once registered, the malicious DLL is invoked automatically whenever the Netsh utility is executed (either manually by a user or programmatically by scripts and system processes). This provides attackers with persistent code execution opportunities.
Stealth and Persistence: Since Netsh is a trusted Windows binary, malicious activity leveraging Netsh helper DLLs can evade detection by traditional antivirus and endpoint security solutions. Attackers may disguise malicious DLLs with legitimate-sounding filenames or store them in inconspicuous directories to further evade detection.
Privilege Requirements: Modifying the registry to register a Netsh helper DLL typically requires administrator-level privileges. Attackers often leverage privilege escalation techniques or exploit vulnerabilities to gain the required permissions.
Attack scenarios and stages where Netsh helper DLL persistence is commonly employed include:
Persistence Stage: Attackers use this technique primarily to maintain persistent access after initial compromise, ensuring continued control even after system reboots.
Post-Exploitation Stage: After gaining initial access or escalating privileges, adversaries implement Netsh helper DLLs to maintain stealthy persistence and execute payloads discretely.
Advanced Persistent Threat (APT) Campaigns: Sophisticated threat actors frequently use this technique in targeted attacks due to its stealth, reliability, and minimal footprint.
Lateral Movement and Long-Term Persistence: Attackers aiming for prolonged presence in compromised networks leverage Netsh helper DLLs across multiple endpoints to establish resilient, long-term footholds.
Detection methods, tools, and indicators of compromise (IoCs) include:
Registry Monitoring: Continuously monitor registry keys related to Netsh helper DLL registration:
HKLM\SOFTWARE\Microsoft\Netsh
HKLM\SOFTWARE\WOW6432Node\Microsoft\Netsh
File Integrity Monitoring (FIM): Implement FIM solutions to detect unauthorized changes or additions of DLL files in system directories, particularly those referenced by Netsh helper DLL registry entries.
Process Monitoring and Logging:
Monitor and log execution events of Netsh processes (netsh.exe) and correlate these events with DLL loading activities. Tools such as Sysmon (System Monitor), Windows Event Logs, and advanced EDR (Endpoint Detection and Response) solutions can detect anomalous behavior.
Behavioral Analysis and Endpoint Detection: Employ endpoint security solutions to detect suspicious DLL loading patterns, especially those involving Netsh. Look for unusual DLL paths or file names not commonly associated with legitimate network configuration tasks.
Indicators of Compromise (IoCs): Specific IoCs include:
Unusual DLL files registered as Netsh helper DLLs.
Suspicious registry entries under Netsh registry keys.
Unexpected network connections initiated by processes spawned from Netsh.
Anomalous DLL file metadata (timestamps, authorship, digital signatures).
Detecting Netsh helper DLL persistence is crucial due to potential impacts on systems and networks, including:
Long-Term Persistence and Stealth: Attackers leveraging this technique maintain persistent, stealthy footholds, complicating remediation efforts and increasing dwell time.
Privilege Escalation and Code Execution: Malicious DLLs loaded via Netsh can execute arbitrary code with elevated privileges, potentially leading to further compromise, data exfiltration, lateral movement, and system disruption.
Evasion of Traditional Security Controls: Because Netsh is a legitimate Windows utility, malicious DLLs loaded via this method often evade antivirus and basic endpoint protection solutions, necessitating proactive detection and threat hunting efforts.
Potential for Data Exfiltration and Damage: Attackers use persistent access to exfiltrate sensitive data, execute ransomware payloads, or disrupt critical services, resulting in financial losses, reputational damage, and operational disruption.
Early detection significantly reduces attacker dwell time, limits damage, and facilitates rapid incident response and remediation.
Real-world examples of Netsh helper DLL abuse include:
APT41 (Winnti Group):
Attackers associated with APT41 used Netsh helper DLL persistence in targeted intrusions against technology, healthcare, and gaming organizations.
Malicious DLLs such as netsh.dll were registered and loaded via Netsh to maintain persistent access.
FIN7 Threat Actor:
FIN7 leveraged Netsh helper DLLs in targeted attacks against financial institutions and retail organizations to maintain stealthy persistence and execute malicious payloads.
Operation ShadowHammer (ASUS Supply Chain Attack):
Attackers used Netsh helper DLL persistence as part of their broader toolkit to maintain persistent access and deliver malicious payloads to compromised endpoints.
Common Attack Scenario:
Attacker gains initial access via phishing or exploitation.
Privilege escalation occurs, granting administrator-level permissions.
Malicious DLL is placed in a legitimate directory or disguised as a legitimate file.
Registry keys are modified to register the malicious DLL as a Netsh helper DLL.
Each time Netsh executes, the malicious DLL is loaded, ensuring persistent execution and stealthy operation.
These examples illustrate the technique's effectiveness in maintaining long-term persistence, executing malicious payloads, and evading traditional security detection mechanisms.