Regsvcs/Regasm
Regsvcs/Regasm [T1218.009]
Last updated
Regsvcs/Regasm [T1218.009]
Last updated
Name: Regsvcs/Regasm
ID: T1218.009
Tactics:
Technique:
Regsvcs and Regasm (T1218.009) is a sub-technique within the MITRE ATT&CK framework, categorized under the parent technique "Signed Binary Proxy Execution" (T1218). This sub-technique leverages legitimate Windows utilities—specifically Regsvcs.exe and Regasm.exe—to execute malicious payloads or scripts while bypassing application whitelisting and security controls. Attackers abuse these trusted binaries to execute arbitrary code, thereby evading detection mechanisms and maintaining stealth during an intrusion.
Regsvcs.exe (Microsoft .NET Services Installation Tool) and Regasm.exe (Assembly Registration Tool) are legitimate Windows utilities provided by Microsoft for registering and unregistering .NET assemblies as COM components. These utilities are typically found in standard Windows installations with the .NET Framework, making them ideal targets for attackers seeking to exploit trusted Windows binaries.
Technical execution methods include:
Regasm.exe:
Normally used to register .NET assemblies into the Global Assembly Cache (GAC).
Attackers can leverage Regasm.exe to load malicious DLLs or execute arbitrary code embedded within .NET assemblies.
Example command:
Regsvcs.exe:
Designed for registering serviced components into COM+ applications.
Threat actors exploit Regsvcs.exe by supplying malicious .NET assemblies that contain embedded payloads.
Example command:
Mechanisms of exploitation include:
Leveraging the inherent trust of signed Microsoft binaries to evade application whitelisting policies.
Utilizing these utilities to execute arbitrary code within the context of trusted processes, thereby reducing suspicion.
Exploiting the ability to load external assemblies and DLLs without triggering standard security alerts.
Real-world procedures involve:
Embedding payloads within .NET assemblies that can execute commands, spawn processes, or establish persistence.
Using these utilities during lateral movement, privilege escalation, or persistence phases in an attack lifecycle.
Employing these methods to evade detection by endpoint protection solutions that rely on signature-based detection or binary whitelisting.
Attackers typically employ Regsvcs/Regasm (T1218.009) in various stages and scenarios, including:
Initial Access and Execution:
Gaining initial foothold by bypassing application whitelisting and endpoint security.
Executing payloads delivered through phishing attacks or malicious downloads.
Defense Evasion:
Evading application whitelisting, antivirus, and EDR solutions that trust signed Microsoft binaries.
Obfuscating malicious activity by blending with legitimate administrative actions.
Persistence:
Establishing persistence by registering malicious assemblies as COM components or services, ensuring execution upon system reboot or user logon.
Privilege Escalation and Lateral Movement:
Executing malicious payloads with higher privileges by leveraging trusted Windows utilities.
Facilitating lateral movement across compromised networks by executing payloads remotely via trusted Windows binaries.
Effective detection strategies for Regsvcs/Regasm (T1218.009) include:
Process Monitoring and Behavioral Analysis:
Monitor and alert on suspicious execution of "regsvcs.exe" and "regasm.exe" from unusual or unauthorized locations.
Detect abnormal parent-child process relationships involving these utilities, such as execution spawned from scripting engines (PowerShell, cmd.exe) or unexpected parent processes.
Command-Line Auditing:
Enable command-line logging and analyze logs for unusual parameters, especially the loading of assemblies from temporary or suspicious directories.
Identify unusual usage of "/U" (unregister) parameters or assembly registrations involving unexpected DLLs.
File System and Registry Monitoring:
Track and alert on suspicious assembly files (.dll files) being written or loaded into sensitive locations, especially temporary folders or user directories.
Monitor registry entries related to COM component registration for suspicious changes or additions.
Endpoint Detection and Response (EDR) Tools:
Utilize EDR solutions capable of detecting anomalous behavior involving trusted Windows binaries.
Leverage threat hunting queries and analytics to identify patterns of misuse of these utilities.
Specific Indicators of Compromise (IoCs) include:
Execution of "regasm.exe" or "regsvcs.exe" from non-standard directories.
Loading of assemblies or DLLs from temporary folders, user profile directories, or network shares.
Unusual command-line parameters or scripts invoking these binaries.
Unexpected COM registrations or service installations in registry keys.
Detecting the misuse of Regsvcs/Regasm (T1218.009) is critical due to several potential impacts:
Bypassing Security Controls:
Attackers leverage trusted Windows utilities to bypass application whitelisting, antivirus, and endpoint security solutions, enabling undetected execution of malicious payloads.
Persistence and Privilege Escalation:
Malicious COM component registration or assembly execution can lead to persistent footholds within compromised environments, complicating remediation efforts.
Stealth and Evasion:
Abuse of legitimate binaries significantly reduces the likelihood of detection by security tools reliant on binary reputation or signature-based detection methods.
Advanced Threat Actor Operations:
Usage is commonly associated with sophisticated threat actors and advanced persistent threats (APTs), indicating high-risk intrusions with potentially severe impacts.
Early detection is crucial to:
Reduce dwell time and limit damage by identifying compromise early in the attack lifecycle.
Prevent escalation of privileges, lateral movement, and further exploitation within the environment.
Enable effective incident response and remediation efforts to mitigate threats before significant harm occurs.
Real-world examples demonstrating the use of Regsvcs/Regasm (T1218.009) include:
APT Groups and Nation-State Actors:
Advanced persistent threat actors have utilized Regasm.exe and Regsvcs.exe to execute malicious payloads, evade detection, and establish persistence within targeted environments.
Notably, groups such as APT29 (Cozy Bear) and APT32 (OceanLotus) have leveraged signed Microsoft binaries, including Regsvcs.exe, to bypass application whitelisting and execute payloads during cyber espionage campaigns.
Red Teaming and Penetration Testing Tools:
Offensive security frameworks, such as Cobalt Strike, Invoke-Obfuscation, and custom PowerShell frameworks, commonly incorporate techniques leveraging Regsvcs and Regasm to bypass defensive controls during penetration tests and red team exercises.
Security researchers frequently demonstrate proof-of-concept (PoC) payloads leveraging these utilities to highlight security gaps and validate detection capabilities.
Malware Campaigns and Commodity Malware:
Malware campaigns employing commodity malware and ransomware have used Regasm.exe and Regsvcs.exe to execute payloads stealthily, bypassing standard antivirus and endpoint detection solutions.
For example, certain malware families have embedded malicious .NET assemblies to be executed via Regasm.exe, facilitating stealthy execution and persistence.
Impacts from these real-world scenarios commonly include:
Establishment of persistent backdoors and remote access Trojans (RATs).
Exfiltration of sensitive data and intellectual property.
Deployment of ransomware payloads resulting in operational disruptions.
Evasion of security controls, complicating detection and remediation efforts.