Verclsid
Verclsid [T1218.012]
Information
Introduction
Verclsid.exe (T1218.012) is a sub-technique under the Signed Binary Proxy Execution technique (T1218) within the MITRE ATT&CK framework. Attackers leverage legitimate, digitally signed Windows binaries like Verclsid.exe to bypass application control mechanisms and execute malicious payloads. Verclsid.exe is a built-in Windows binary designed to verify shell extensions before they are instantiated by Windows Explorer, making it a trusted and stealthy vector for adversaries to abuse during intrusion attempts.
Deep Dive Into Technique
Verclsid.exe is a legitimate Windows executable located typically at %SystemRoot%\System32\verclsid.exe. Its primary purpose is to validate shell extensions and COM objects, ensuring their integrity before Windows Explorer loads them. Because this binary is digitally signed and native to Windows, it is frequently allowed to execute by application control solutions and antivirus software, making it an attractive target for adversaries.
Attackers typically exploit Verclsid.exe by manipulating registry entries associated with COM objects or shell extensions. Specifically, adversaries may:
Modify registry keys under
HKCU\Software\Classes\CLSIDorHKLM\Software\Classes\CLSIDto reference malicious DLLs or payloads.Invoke Verclsid.exe with specific CLSID parameters, forcing it to load and execute attacker-controlled DLLs.
Utilize command-line syntax such as:
Where
{CLSID_GUID}points to a malicious COM object defined by the attacker.
This technique leverages DLL side-loading or DLL hijacking to execute malicious code under the context of a trusted Windows binary. Because Verclsid.exe is digitally signed by Microsoft, defensive tools often overlook its execution, allowing attackers to evade detection and establish persistence or execute payloads stealthily.
When this Technique is Usually Used
Attackers commonly use Verclsid.exe in multiple stages and scenarios across cyber-attacks, including:
Initial Access and Execution Stage: To bypass application whitelisting and execute payloads after initial compromise.
Defense Evasion Stage: To evade antivirus and endpoint detection and response (EDR) solutions by executing malicious code via a trusted binary.
Persistence Stage: To establish persistent backdoors by registering malicious COM objects or shell extensions in Windows registry.
Privilege Escalation Stage: To exploit misconfigured permissions on registry keys or DLL locations, potentially elevating privileges.
Typical attack scenarios include:
Advanced Persistent Threat (APT) campaigns targeting high-value networks.
Malware infections attempting to evade detection and establish long-term persistence.
Red team operations simulating adversary tradecraft to assess defensive capabilities.
How this Technique is Usually Detected
Detection of Verclsid.exe abuse can be challenging due to its legitimate nature. However, defenders can employ various detection methods and indicators of compromise (IoCs):
Process Monitoring and Logging:
Monitor and log execution of Verclsid.exe processes.
Scrutinize command-line parameters passed to Verclsid.exe, especially unusual CLSID GUIDs or uncommon switches.
Registry Monitoring:
Detect and alert on unauthorized changes to registry keys under:
HKCU\Software\Classes\CLSID\HKLM\Software\Classes\CLSID\
Identify suspicious CLSID registrations referencing unknown or unsigned DLLs.
DLL Monitoring and Integrity Checks:
Monitor DLL load events associated with Verclsid.exe processes.
Investigate DLLs loaded from unexpected directories or those not digitally signed by trusted vendors.
Endpoint Detection and Response (EDR) and SIEM Tools:
Implement behavioral detection rules identifying unusual Verclsid.exe execution patterns.
Correlate events across multiple endpoints to identify anomalous usage patterns indicative of compromise.
Specific Indicators of Compromise (IoCs):
Unexpected execution of Verclsid.exe with uncommon CLSID GUIDs.
DLLs loaded by Verclsid.exe from temporary directories (
%TEMP%), user directories, or other suspicious paths.Unusual network connections initiated by processes spawned by Verclsid.exe.
Why it is Important to Detect This Technique
Detecting malicious use of Verclsid.exe is crucial due to the potential severity of impacts on systems and networks:
Bypassing Security Controls: Attackers leverage trusted binaries, circumventing application whitelisting, antivirus, and EDR solutions, significantly reducing security effectiveness.
Persistence and Long-Term Compromise: Registry-based persistence via COM objects or shell extensions allows attackers to maintain ongoing access to compromised systems.
Privilege Escalation and Lateral Movement: Exploitation of registry permissions or DLL hijacking can lead to privilege escalation, enabling attackers to gain administrative privileges and move laterally within networks.
Stealth and Evasion: The legitimate nature of Verclsid.exe execution can delay detection, allowing attackers extended periods of undetected operation within the environment.
Early detection and response to this technique significantly reduces risk, limits attacker dwell time, and prevents severe impacts like data exfiltration, ransomware deployment, or extensive lateral movement.
Examples
Real-world examples demonstrating the abuse of Verclsid.exe include:
APT29 (Cozy Bear) Campaign:
Scenario: APT29 leveraged Verclsid.exe to execute malicious DLLs during intrusion operations against sensitive government networks.
Tools Used: Custom DLL payloads, registry manipulation scripts.
Impact: Persistent access, stealthy execution, evasion of endpoint defenses, and prolonged espionage activities.
FIN7 Threat Group Attacks:
Scenario: FIN7 attackers used Verclsid.exe to load malicious DLLs for persistence and lateral movement within corporate networks.
Tools Used: Commercially available penetration testing frameworks, custom DLL payloads, registry manipulation tools.
Impact: Financial data theft, credit card information compromise, extensive lateral movement, and prolonged access to compromised environments.
Red Team Engagements:
Scenario: Security teams frequently use Verclsid.exe abuse techniques during penetration tests and red team exercises to simulate advanced adversary tradecraft.
Tools Used: Metasploit Framework, Cobalt Strike, custom DLL payloads, registry modification scripts.
Impact: Demonstration of defense evasion capabilities, identification of gaps in endpoint detection and response coverage, and improvement of defensive posture.
These examples highlight the practical threat posed by Verclsid.exe abuse and underscore the importance of robust detection and mitigation strategies.
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