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Cyber ResilienceOrganizations worldwide rely on the Server Message Block (SMB) protocol via TCP port 445 for file sharing, printer access, and process communication. However, security professionals authorized for penetration testing often encounter significant obstacles when attempting lateral movement through NTLM relay attacks targeting this port. Traditional methods, which involve extracting NT hashes from registry hives, are increasingly blocked by modern endpoint detection systems, leading researchers to explore alternative techniques.
Port 445 is a network port used by SMB, necessary for accessing shared network resources. Operating at the application layer, SMB enables nodes in a network to communicate, share files, and use shared services like printers and directories. It is fundamental for intra-network communication and resource sharing, especially in Windows-based networks.
This port replaced earlier SMB versions that used ports 137, 138, and 139 over NetBIOS. Microsoft adopted port 445 for SMB traffic with the release of Windows 2000.
The Core Challenge
When executing NTLM relay attacks against SMB services, attackers face a fundamental constraint: all subsequent actions must operate exclusively through port 445/TCP. This restriction eliminates the possibility of using Windows Management Instrumentation (WMI), which requires additional connectivity through port 135/TCP for Remote Procedure Call (RPC) functionality.
Security researchers typically overcome this limitation by dumping local account credentials from the Security Account Manager (SAM) database. Once extracted, these NT hashes enable authentication to multiple protocols, including WMI, Remote Desktop Protocol (RDP), and Windows Remote Management (WinRM). However, this approach generates substantial noise within monitored environments:
- EDR solutions consistently detect registry hive extraction attempts
- Alert systems trigger immediately upon SAM database access
- Stealth operations become nearly impossible using traditional methods
The question becomes: How can security professionals maintain administrative access while avoiding detection and expanding beyond port 445 limitations?
Service Control Manager: The Gateway Solution
Recent research demonstrates that the Service Control Manager (SCM) provides an effective pathway for expanding attack capabilities while maintaining operational security. The SCM operates entirely through SMB, making it ideal for scenarios where connectivity remains restricted to port 445/TCP.
Unlike registry extraction tools that generate multiple EDR alerts, SCM manipulation through native Windows utilities produces minimal detection signatures. Tools such as services.msc MMC snap-in and sc.exe command-line utility perform identical functions to more detectable frameworks while maintaining stealth characteristics.
Implementation Through SOCKS Proxy
Modern NTLM relay tools support SOCKS proxy functionality, allowing persistent authentication sessions without repeated attack execution. This capability enables thorough testing of various lateral movement techniques while preserving the established administrative context.
Configuration involves several key steps:
- Establish Relay Session: Configure ntlmrelayx.py with the –socks flag to maintain active authentication
- Verify Port Requirements: Monitor debug output to confirm exclusive port 445/TCP usage
- Proxy Native Tools: Route legitimate Windows utilities through the established SOCKS connection
This approach eliminates the signature patterns associated with penetration testing frameworks while providing identical functionality through Microsoft-signed binaries.
Organizations worldwide rely on the Server Message Block (SMB) protocol via TCP port 445 for file sharing, printer access, and process communication. However, security professionals authorized for penetration testing often encounter significant obstacles when attempting lateral movement through NTLM relay attacks targeting this port. Traditional methods, which involve extracting NT hashes from registry hives, are increasingly blocked by modern endpoint detection systems, leading researchers to explore alternative techniques.
Port 445 is a network port used by SMB, necessary for accessing shared network resources. Operating at the application layer, SMB enables nodes in a network to communicate, share files, and use shared services like printers and directories. It is fundamental for intra-network communication and resource sharing, especially in Windows-based networks.
This port replaced earlier SMB versions that used ports 137, 138, and 139 over NetBIOS. Microsoft adopted port 445 for SMB traffic with the release of Windows 2000.
The Core Challenge
When executing NTLM relay attacks against SMB services, attackers face a fundamental constraint: all subsequent actions must operate exclusively through port 445/TCP. This restriction eliminates the possibility of using Windows Management Instrumentation (WMI), which requires additional connectivity through port 135/TCP for Remote Procedure Call (RPC) functionality.
Security researchers typically overcome this limitation by dumping local account credentials from the Security Account Manager (SAM) database. Once extracted, these NT hashes enable authentication to multiple protocols, including WMI, Remote Desktop Protocol (RDP), and Windows Remote Management (WinRM). However, this approach generates substantial noise within monitored environments:
- EDR solutions consistently detect registry hive extraction attempts
- Alert systems trigger immediately upon SAM database access
- Stealth operations become nearly impossible using traditional methods
The question becomes: How can security professionals maintain administrative access while avoiding detection and expanding beyond port 445 limitations?
Service Control Manager: The Gateway Solution
Recent research demonstrates that the Service Control Manager (SCM) provides an effective pathway for expanding attack capabilities while maintaining operational security. The SCM operates entirely through SMB, making it ideal for scenarios where connectivity remains restricted to port 445/TCP.
Unlike registry extraction tools that generate multiple EDR alerts, SCM manipulation through native Windows utilities produces minimal detection signatures. Tools such as services.msc MMC snap-in and sc.exe command-line utility perform identical functions to more detectable frameworks while maintaining stealth characteristics.
Implementation Through SOCKS Proxy
Modern NTLM relay tools support SOCKS proxy functionality, allowing persistent authentication sessions without repeated attack execution. This capability enables thorough testing of various lateral movement techniques while preserving the established administrative context.
Configuration involves several key steps:
- Establish Relay Session: Configure ntlmrelayx.py with the –socks flag to maintain active authentication
- Verify Port Requirements: Monitor debug output to confirm exclusive port 445/TCP usage
Proxy Native Tools: Route legitimate Windows utilities through the established SOCKS connection.
This approach eliminates the signature patterns associated with penetration testing frameworks while providing identical functionality through Microsoft-signed binaries.
The WebClient Service: Unlocking Protocol Flexibility
The most significant breakthrough in escaping port 445 restrictions involves manipulating the WebClient service on target systems. This Windows component enables WebDAV functionality, which fundamentally changes how authentication coercion behaves during subsequent attacks.
Traditional authentication coercion techniques produce NetNTLMv2 hashes encapsulated within SMB packets. These authentication attempts cannot be relayed to Lightweight Directory Access Protocol (LDAP) services due to protocol restrictions. However, when the WebClient service operates on the target system, authentication coercion generates WebDAV-formatted requests instead.
WebDAV operates as an HTTP-based protocol, making it compatible with LDAP relay attacks. This compatibility enables two powerful computer account takeover techniques:
Resource-Based Constrained Delegation (RBCD)
RBCD attacks manipulate Active Directory attributes to grant delegation rights to attacker-controlled accounts. Once established, these rights enable impersonation of high-privilege accounts without requiring password knowledge.
Shadow Credentials Attack
Shadow Credentials involves adding attacker-controlled certificate information to target computer accounts. This technique enables authentication as the compromised system using legitimate Kerberos protocols.
Technical Implementation Process
The complete attack chain requires careful orchestration of multiple components:
Phase 1: Initial Access
- Execute NTLM relay attack targeting SMB service
- Establish SOCKS proxy connection for persistent access
- Verify administrative privileges on target system
Phase 2: Service Manipulation
- Connect to the target SCM through an authenticated session
- Enable WebClient service using native Windows tools
- Confirm service activation without triggering alerts
Phase 3: Protocol Expansion
- Perform authentication coercion against WebClient-enabled target
- Capture WebDAV-formatted authentication requests
- Relay authentication to the domain controller LDAP service
Phase 4: Account Takeover
- Execute RBCD or Shadow Credentials attack
- Establish persistent access to target computer account
- Enable broader lateral movement capabilities
Operational Security Considerations
Successful implementation requires attention to several critical factors:
Detection Avoidance: Native Windows utilities generate significantly fewer EDR alerts compared to third-party penetration testing tools. However, service manipulation activities may still produce audit logs requiring careful timing and operational planning.
LDAP Prerequisites: Target domain controllers must lack LDAP signing enforcement or channel binding protections. While these security measures are becoming more common, many organizations still operate with vulnerable configurations.
Service Dependencies: WebClient service activation may impact system performance or stability. Security professionals should understand potential operational effects before implementation.
Real-World Application Scenarios
This technique proves particularly valuable in several common engagement scenarios:
Corporate Network Assessments: Organizations with robust EDR deployments that block traditional credential extraction methods require alternative approaches. Service manipulation provides effective lateral movement without triggering defensive systems.
Red Team Operations: Long-term engagements benefit from persistent access methods that avoid detection. The WebClient technique enables sustained network presence while maintaining operational security. Organizations seeking comprehensive red team assessment services can leverage these advanced techniques to thoroughly evaluate their defensive capabilities.
Compliance Testing: Regulatory frameworks often require demonstration of lateral movement capabilities. This approach satisfies compliance requirements while respecting organizational security investments.
Defensive Recommendations
Security teams should implement multiple layers of protection against these advanced techniques:
SMB Hardening: Enforce SMB signing requirements across all systems to prevent NTLM relay attacks. Disable legacy SMB versions that lack modern security features.
Service Monitoring: Deploy monitoring solutions that track service state changes, particularly for security-sensitive services like WebClient. Unusual activation patterns may indicate compromise.
LDAP Security: Enable LDAP signing and channel binding on all domain controllers. These protections prevent credential relay attacks regardless of the initial compromise method.
Network Segmentation: Implement micro-segmentation to limit lateral movement possibilities. Even a successful account compromise should face additional network barriers.
Conclusion
The evolution of endpoint security pushes security professionals to develop more sophisticated attack methods. Traditional SMB port bypasses relied on noisy credential extraction, but modern methods use legitimate Windows functions for stealth.
Using Service Control Manager manipulation and WebClient service activation improves lateral movement. Understanding these techniques and defenses helps organizations assess risks and develop strategies.
Effective security must go beyond signature detection, addressing protocol vulnerabilities and not just behavioral analysis. Attackers will find alternative paths, so security must eliminate vulnerabilities and implement defense-in-depth strategies that work even if controls are bypassed.
The WebClient Service: Unlocking Protocol Flexibility
The most significant breakthrough in escaping port 445 restrictions involves manipulating the WebClient service on target systems. This Windows component enables WebDAV functionality, which fundamentally changes how authentication coercion behaves during subsequent attacks.
Traditional authentication coercion techniques produce NetNTLMv2 hashes encapsulated within SMB packets. These authentication attempts cannot be relayed to Lightweight Directory Access Protocol (LDAP) services due to protocol restrictions. However, when the WebClient service operates on the target system, authentication coercion generates WebDAV-formatted requests instead.
WebDAV operates as an HTTP-based protocol, making it compatible with LDAP relay attacks. This compatibility enables two powerful computer account takeover techniques:
Resource-Based Constrained Delegation (RBCD)
RBCD attacks manipulate Active Directory attributes to grant delegation rights to attacker-controlled accounts. Once established, these rights enable impersonation of high-privilege accounts without requiring password knowledge.
Shadow Credentials Attack
Shadow Credentials involves adding attacker-controlled certificate information to target computer accounts. This technique enables authentication as the compromised system using legitimate Kerberos protocols.
Technical Implementation Process
The complete attack chain requires careful orchestration of multiple components:
Phase 1: Initial Access
- Execute NTLM relay attack targeting SMB service
- Establish SOCKS proxy connection for persistent access
- Verify administrative privileges on target system
Phase 2: Service Manipulation
- Connect to the target SCM through an authenticated session
- Enable WebClient service using native Windows tools
- Confirm service activation without triggering alerts
Phase 3: Protocol Expansion
- Perform authentication coercion against WebClient-enabled target
- Capture WebDAV-formatted authentication requests
- Relay authentication to the domain controller LDAP service
Phase 4: Account Takeover
- Execute RBCD or Shadow Credentials attack
- Establish persistent access to target computer account
- Enable broader lateral movement capabilities
Operational Security Considerations
Successful implementation requires attention to several critical factors:
Detection Avoidance: Native Windows utilities generate significantly fewer EDR alerts compared to third-party penetration testing tools. However, service manipulation activities may still produce audit logs requiring careful timing and operational planning.
LDAP Prerequisites: Target domain controllers must lack LDAP signing enforcement or channel binding protections. While these security measures are becoming more common, many organizations still operate with vulnerable configurations.
Service Dependencies: WebClient service activation may impact system performance or stability. Security professionals should understand potential operational effects before implementation.
Real-World Application Scenarios
This technique proves particularly valuable in several common engagement scenarios:
Corporate Network Assessments: Organizations with robust EDR deployments that block traditional credential extraction methods require alternative approaches. Service manipulation provides effective lateral movement without triggering defensive systems.
Red Team Operations: Long-term engagements benefit from persistent access methods that avoid detection. The WebClient technique enables sustained network presence while maintaining operational security. Organizations seeking comprehensive red team assessment services can leverage these advanced techniques to thoroughly evaluate their defensive capabilities.
Compliance Testing: Regulatory frameworks often require demonstration of lateral movement capabilities. This approach satisfies compliance requirements while respecting organizational security investments.
Defensive Recommendations
Security teams should implement multiple layers of protection against these advanced techniques:
SMB Hardening: Enforce SMB signing requirements across all systems to prevent NTLM relay attacks. Disable legacy SMB versions that lack modern security features.
Service Monitoring: Deploy monitoring solutions that track service state changes, particularly for security-sensitive services like WebClient. Unusual activation patterns may indicate compromise.
LDAP Security: Enable LDAP signing and channel binding on all domain controllers. These protections prevent credential relay attacks regardless of the initial compromise method.
Network Segmentation: Implement micro-segmentation to limit lateral movement possibilities. Even a successful account compromise should face additional network barriers.
Conclusion
The evolution of endpoint security pushes security professionals to develop more sophisticated attack methods. Traditional SMB port bypasses relied on noisy credential extraction, but modern methods use legitimate Windows functions for stealth.
Using Service Control Manager manipulation and WebClient service activation improves lateral movement. Understanding these techniques and defenses helps organizations assess risks and develop strategies.
Effective security must go beyond signature detection, addressing protocol vulnerabilities and not just behavioral analysis. Attackers will find alternative paths, so security must eliminate vulnerabilities and implement defense-in-depth strategies that work even if controls are bypassed.
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