Network Pivoting (Port Redirection and Tunneling)

In today’s interconnected world, network security is of utmost importance. As technology advances, so do the techniques employed by cybercriminals to gain unauthorized access to sensitive data and resources. One such technique that has become increasingly prevalent is “Network Pivoting.” Imagine an intruder managing to slip through the defenses of a well-secured network, but instead of stopping there, they continue to maneuver undetected, seeking out more valuable targets within the network’s fortress. This is precisely what network pivoting enables – the ability to move laterally within a network, expanding the reach of an attack and potentially wreaking havoc on an organization’s digital infrastructure.

But network pivoting is not just a tool for malicious actors. Ethical hackers and cybersecurity professionals also employ it as part of penetration testing and security assessments to identify vulnerabilities and weaknesses in a network’s defenses. Understanding network pivoting is essential for both defenders and security practitioners to defend against potential threats and maintain robust security measures.

In this article, we will take a deep dive into the world of network pivoting. We will explore its fundamental concepts, the types of techniques employed, and the risks and challenges it poses. Additionally, we’ll examine the common tunneling protocols and port redirection techniques used to facilitate network pivoting. Furthermore, we’ll shed light on some of the prevalent tools leveraged by attackers and security professionals alike to execute network pivoting. However, it is essential to remember that these techniques can be harmful if misused or employed without proper authorization.

Understanding network pivoting

Network pivoting refers to the technique of using compromised or unauthorized access to one network or system as a springboard to gain access to other networks or systems within the same infrastructure. It involves redirecting network traffic or establishing tunnels to bypass security measures and move laterally across the network.

To understand network pivoting, let’s consider an analogy of a physical office building. Imagine you have unauthorized access to one office on a particular floor, but you want to gain access to another office on a different floor without being detected. Instead of walking through the main entrance and attracting attention, you might find alternative routes, such as hidden passages or tunnels, to navigate through the building and reach your desired destination.

In the context of computer networks, network pivoting follows a similar principle. When an attacker gains control over a compromised system within a target network, they can use it as a launching point to explore and attack other systems within the network. By leveraging network pivoting techniques, they can avoid triggering alarms or arousing suspicion.

Types of network pivoting techniques

There are several types of network pivoting techniques that attackers and security professionals employ to gain unauthorized access or test the security of a network. Let’s explore each technique in-depth:

1. Port Forwarding:

Port forwarding, also known as port redirection, involves redirecting network traffic from one port on a compromised system to another port on a different system within the target network. This technique allows attackers to access services or resources that are typically hidden or inaccessible from outside the network. Here’s how it works:

An attacker gains control over a compromised system within the target network.
They configure the compromised system to listen on a specific port.
Incoming network traffic targeting that port is redirected to a different system and port within the network.
The attacker can then communicate with the redirected service or resource on the internal system as if they were directly accessing it.

Port forwarding is commonly used to bypass firewall restrictions or access internal services that are not exposed to the external network. However, it can also be used by security professionals for legitimate purposes, such as remote administration or accessing resources in a secure manner.

2. Reverse SSH Tunneling:

Reverse SSH tunneling is a technique where an attacker establishes an encrypted tunnel from the compromised system back to their own system outside the target network. This tunnel allows the attacker to bypass firewalls and access services on the compromised system as if they were locally present. The process of reverse SSH tunneling involves the following steps:

The attacker initiates a connection from the compromised system to their own system outside the target network using SSH.
The connection is established in reverse, with the compromised system acting as the SSH client and the attacker’s system as the SSH server.
Once the tunnel is established, the attacker can access services on the compromised system by connecting to the tunnel endpoint on their own system.

Reverse SSH tunneling is effective in scenarios where direct inbound connections to the compromised system are blocked or restricted. It allows attackers to bypass network security measures and gain remote access to internal resources.

3. Proxy Pivoting:

Proxy pivoting involves configuring the compromised system as a proxy server to relay network traffic between external systems and internal systems within the target network. By acting as an intermediary, the compromised system disguises the attacker’s true identity and location. Here’s how proxy pivoting works:

The attacker sets up the compromised system as a proxy server, configuring it to accept incoming network connections.
External systems connect to the compromised system, believing it to be a legitimate proxy server.
The compromised system relays the network traffic between the external systems and internal systems within the target network.
This allows the attacker to access internal resources and services indirectly through the compromised system, effectively hiding their presence.

Proxy pivoting enables attackers to bypass network restrictions, evade detection, and carry out activities as if they were coming from within the target network.

4. VPN Pivoting:

VPN pivoting involves using the compromised system as a Virtual Private Network (VPN) gateway to establish a secure connection to the target network. By leveraging the compromised system as an entry point, the attacker can gain access to the network as if they were physically present within it. The process of VPN pivoting typically follows these steps:

The attacker configures the compromised system to act as a VPN server or gateway.
They establish a VPN connection from their own system to the compromised system, creating a secure tunnel.
Once the VPN tunnel is established, the attacker’s system is virtually connected to the target network.
The attacker can then access network resources and services as if they were connected directly to the target network.

VPN pivoting enables attackers to bypass perimeter defenses and gain remote access to internal network resources securely.

It’s important to note that while these network pivoting techniques are discussed in the context of potential malicious activities, they can also be utilized by legitimate security professionals for network testing, troubleshooting, and securing network infrastructure.

Port Redirection Techniques

Port redirection techniques, also known as port forwarding, are used in network pivoting to redirect network traffic from one port on a compromised system to another port on a different system within the network. This enables attackers or security professionals to access services or resources that are typically inaccessible or hidden from external networks. Let’s explore the different types of port redirection techniques:

Local Port Forwarding:

Local port forwarding allows an attacker or user to redirect traffic from a local port on their system to a remote system within the network. It establishes a secure tunnel between the local system and the remote system, allowing the user to access services running on the remote system through their own machine. Here’s how local port forwarding works:

The attacker initiates a connection to the compromised system.
They configure the local system to listen on a specific port.
Incoming traffic to the local port is encrypted and forwarded through the secure tunnel to the remote system.
The remote system then processes the traffic and sends the response back through the tunnel to the local system.
The user can access the service running on the remote system as if it were running locally on their own system.

Local port forwarding is commonly used in scenarios where the attacker wants to access resources within the network that are only accessible from the compromised system. It allows the attacker to leverage their access to the compromised system to reach other systems or services within the network.

Remote Port Forwarding:

Remote port forwarding enables an attacker or user to redirect traffic from a remote port on the compromised system to a local port on their own system. This technique allows the user to access services or resources running on their system through the compromised system within the network. Here’s how remote port forwarding works:

The attacker initiates a connection to the compromised system.
They configure the compromised system to listen on a specific port.
Incoming traffic to the remote port is encrypted and forwarded through the secure tunnel to the local system.
The local system processes the traffic and sends the response back through the tunnel to the remote system.
The user can access the service running on their local system as if it were running on the compromised system within the network.

Remote port forwarding is often used when the user wants to expose services on their local system to the network where the compromised system is located. It allows the user to bypass network restrictions and access their local services through the compromised system.

Dynamic Port Forwarding:

Dynamic port forwarding, also known as dynamic SOCKS proxy, is a more versatile port redirection technique. It allows the attacker or user to create a SOCKS proxy server on the compromised system, which can forward traffic to various destinations within the network. Here’s how dynamic port forwarding works:

The attacker initiates a connection to the compromised system.
They configure the compromised system to act as a SOCKS proxy server.
Applications or tools on the local system are configured to use the SOCKS proxy server.
When the local applications make network requests, the traffic is forwarded through the SOCKS proxy to the compromised system.
The compromised system then routes the traffic to the appropriate destination within the network.

Dynamic port forwarding provides flexibility as it allows the user to access multiple resources or services within the network through a single SOCKS proxy server on the compromised system.

Port redirection techniques are essential for network pivoting as they enable attackers or security professionals to bypass network restrictions, access internal services, and move laterally within a network. It’s crucial to understand and secure against these techniques to prevent unauthorized access and protect sensitive resources.

Tunneling Protocols

Tunneling is a technique used in networking to encapsulate one network protocol within another network protocol. It allows data from one network to travel securely through another network, even if the two networks have different protocols or security configurations. Tunneling creates a virtual “tunnel” or pathway for the encapsulated data to pass through the intermediate network.

In a tunneling scenario, the original data packets from the source network are encapsulated within new packets that conform to the protocol of the intermediate network. These new packets are then transmitted through the intermediate network to the destination network, where they are decapsulated to retrieve the original data.

Tunneling provides several benefits and use cases:

Security: Tunneling protocols, such as SSL/TLS and IPsec, offer encryption and authentication mechanisms that enhance the security of transmitted data. By encapsulating the data within secure packets, tunneling helps protect against unauthorized access and eavesdropping.
Network Compatibility: Tunneling enables communication between networks that may use different protocols or have incompatible network configurations. It allows data to traverse networks with different addressing schemes, routing protocols, or security measures.
Remote Access: Tunneling protocols, such as SSH and VPNs, facilitate secure remote access to private networks or systems. Users can establish encrypted tunnels to securely access resources within a network from a remote location.
Bypassing Restrictions: Tunneling can be used to bypass network restrictions imposed by firewalls or other security measures. By encapsulating data within packets that are allowed through the network, users can access resources that would otherwise be blocked.
Private Networking: Tunneling protocols, like PPTP and L2TP, enable the creation of virtual private networks (VPNs). VPNs provide a secure and private connection over public networks, allowing users to connect securely to a remote network as if they were physically present within it.

Tunneling involves two key components:

Tunneling Protocol: This is the protocol used to encapsulate the original data packets within new packets that conform to the intermediate network’s protocol. Examples of tunneling protocols include SSH, SSL/TLS, IPsec, PPTP, and L2TP.
Tunnel Endpoints: These are the points where the encapsulation and decapsulation of data occur. The source and destination systems or networks serve as the tunnel endpoints. The encapsulated data enters the tunnel at the source endpoint, travels through the intermediate network, and is decapsulated at the destination endpoint.

Tunneling is a versatile technique that allows for secure and efficient communication between networks, regardless of their differences in protocols, configurations, or security measures. It provides a means to extend network connectivity, enhance security, and enable remote access to resources.

Common tunneling protocols

There are several common tunneling protocols used in networking to establish secure and encrypted tunnels for transmitting data between systems or networks. Let’s explore some of these protocols in-depth:

1. Secure Shell (SSH) Tunneling:

SSH tunneling, also known as SSH port forwarding, is a widely used tunneling protocol that leverages the SSH protocol for secure communication. SSH tunneling allows users to create encrypted tunnels between their local system and a remote system. SSH supports three types of tunneling:

Local Port Forwarding: It forwards traffic from a local port on the user’s system to a remote destination within the network.
Remote Port Forwarding: It forwards traffic from a remote port on the remote system to a local destination on the user’s system.
Dynamic Port Forwarding: It creates a dynamic SOCKS proxy on the user’s system, allowing access to multiple remote resources through a single tunnel. SSH tunneling provides a secure method for accessing resources within a network, bypassing network restrictions, and enhancing the privacy of data transmission.

2. Secure Sockets Layer/Transport Layer Security (SSL/TLS):

SSL and its successor TLS are cryptographic protocols used for securing communication over the internet. They establish an encrypted tunnel between a client and a server, ensuring the confidentiality, integrity, and authenticity of data. SSL/TLS tunneling is commonly used in web applications, where the SSL/TLS protocol secures the communication between a client’s web browser and a web server. It encrypts the data exchanged during the session and provides protection against eavesdropping and tampering. SSL/TLS can also be used to establish virtual private networks (VPNs) for secure remote access to private networks or systems.

3. Internet Protocol Security (IPsec):

IPsec is a suite of protocols used for securing IP communications. It provides authentication, encryption, and integrity protection for IP packets, ensuring secure communication over IP networks. IPsec can be used to create secure tunnels between systems or networks, establishing VPN connections. It encrypts the data at the IP packet level and encapsulates it within IPsec headers, protecting it from unauthorized access or tampering. IPsec is widely used for remote access VPNs, site-to-site VPNs, and securing communication between network devices.

4. Point-to-Point Tunneling Protocol (PPTP):

PPTP is a tunneling protocol commonly used for creating VPN connections. It operates at the data link layer of the OSI model and provides encryption and encapsulation for point-to-point connections. PPTP encapsulates IP packets within Generic Routing Encapsulation (GRE) packets, enabling them to traverse through networks that do not support PPTP directly. It is supported by a wide range of operating systems and is relatively easy to configure. However, PPTP has some security vulnerabilities and is considered less secure compared to other tunneling protocols like IPsec or SSL/TLS.

5. Layer 2 Tunneling Protocol (L2TP):

L2TP is another tunneling protocol commonly used for creating VPN connections. It operates at the data link layer and combines the best features of PPTP and Cisco’s Layer 2 Forwarding (L2F) protocol. L2TP provides a secure tunnel for transmitting data over IP networks. It encapsulates data using IPsec encryption, providing a high level of security. L2TP is often used in combination with IPsec (L2TP/IPsec) to establish VPN connections for secure remote access or site-to-site connectivity.

These common tunneling protocols offer various features and security levels, making them suitable for different network environments and use cases. It’s important to consider the specific requirements and security needs when choosing a tunneling protocol for a particular scenario.

Network Pivoting Tools and Techniques

Network pivoting tools and techniques are utilized by attackers and security professionals to move laterally within a network, gaining access to additional systems and resources. These tools and techniques leverage compromised systems as pivot points to facilitate unauthorized access to other parts of the network. It’s important to note that network pivoting can be used maliciously, but it is also employed by cybersecurity professionals for legitimate purposes like testing network security and identifying vulnerabilities. Here are some common network pivoting tools and techniques:

Metasploit Framework:
Metasploit is a widely used penetration testing framework that includes a variety of network pivoting modules. It allows security professionals to exploit vulnerabilities in target systems, gain access, and then pivot to other systems within the network. Metasploit provides a range of payloads and post-exploitation modules for lateral movement.
Cobalt Strike:
Cobalt Strike is a powerful post-exploitation tool used in red teaming and penetration testing. It enables attackers to simulate advanced threat actor tactics and pivot between systems. Cobalt Strike provides features like Beacon implants for maintaining persistence, lateral movement tools, and social engineering campaigns.
Proxychains:
Proxychains is a command-line tool that allows users to chain multiple proxy servers to tunnel network traffic through intermediate systems. It enables the user to hide their identity and location while accessing remote resources through the compromised system.
SSH Tunneling:
As mentioned earlier, SSH tunneling is not only a pivoting technique but also a legitimate way for administrators to access resources securely within a network. Attackers can use SSH tunneling to create secure channels for pivoting and lateral movement.
Remote Desktop Protocol (RDP) Gateway:
Attackers can exploit RDP gateways that allow remote access to systems within a network. Once they gain access to a system with RDP privileges, they can use the gateway to pivot to other systems within the network.
VPN Pivoting:
If an attacker gains access to a system with VPN access to the corporate network, they can use this system to establish a VPN connection and pivot to other systems within the network. This is why securing remote access points is crucial in network security.
DNS Tunneling:
DNS tunneling involves sending data over DNS queries and responses. Attackers can use this technique to bypass firewalls and exfiltrate data from the compromised system to an external server.
IPv6 Transition Mechanisms:
In networks where both IPv4 and IPv6 are deployed, attackers can exploit IPv6 transition mechanisms (e.g., 6to4, Teredo) to pivot between IPv4 and IPv6 networks, potentially bypassing security controls.

It is important to remember that using these tools and techniques for unauthorized access to networks or systems is illegal and unethical. Ethical hacking, penetration testing, and network security assessments should only be conducted with proper authorization and in compliance with applicable laws and regulations.

Risks and challenges of network pivoting

Network pivoting introduces several risks and challenges that both attackers and defenders need to consider. Understanding these risks is crucial for implementing effective security measures. Here are some of the key risks and challenges associated with network pivoting:

Increased Attack Surface: Network pivoting expands the attack surface by allowing attackers to move laterally within a network. Once an attacker gains access to a system, they can pivot to other systems, potentially compromising a larger number of targets. This increases the potential impact and damage they can inflict on the network.
Privilege Escalation: Network pivoting often involves escalating privileges within the network. Once an attacker gains access to a compromised system, they may attempt to escalate their privileges to gain administrative control over other systems or network resources. Privilege escalation can result in unauthorized access to sensitive data, systems, or services.
Detection and Monitoring Challenges: Network pivoting can be challenging to detect because attackers are leveraging legitimate access credentials or compromised systems. Traditional security measures, such as network firewalls or intrusion detection systems, may not be effective in identifying lateral movement within the network. Detecting and monitoring network pivoting requires advanced security controls and techniques, such as network behavior analysis, anomaly detection, and endpoint security solutions.
Data Exfiltration: Once an attacker has pivoted to multiple systems within a network, they can exfiltrate sensitive data. This poses a significant risk to the organization’s intellectual property, customer information, financial data, and other critical assets. Detecting and preventing data exfiltration during network pivoting requires robust data loss prevention measures and network traffic monitoring.
Persistence and Backdoors: Network pivoting allows attackers to establish persistence within the network by creating backdoors or installing malware on compromised systems. These persistent footholds enable attackers to maintain access even if the initial point of compromise is discovered and remediated. Identifying and removing these backdoors is challenging and requires a thorough investigation and security analysis.
Insider Threats: Network pivoting can exploit insider access or compromised user credentials, making it difficult to distinguish between legitimate user activity and malicious actions. Insiders with authorized access to systems or networks can leverage their privileges to pivot and carry out unauthorized activities. Monitoring user behavior, implementing access controls, and educating employees about the risks of insider threats are essential to mitigate this challenge.
Complex Network Infrastructure: Network pivoting can be more challenging in complex network environments with multiple subnets, segmented networks, or network devices with stringent security controls. Moving laterally across these complex infrastructures requires advanced knowledge of network architecture, routing, and security measures. Organizations need to ensure proper network segmentation, access controls, and monitoring to minimize the impact of network pivoting.
Legal and Ethical Implications: Engaging in unauthorized network pivoting activities is illegal and unethical. Organizations conducting penetration testing or red teaming exercises must have proper authorization and adhere to legal and ethical guidelines. Unauthorized network pivoting can result in legal consequences, damage to reputations, and violation of privacy and security regulations.

To mitigate the risks and challenges associated with network pivoting, organizations should implement a comprehensive set of security measures, including strong access controls, network segmentation, monitoring and detection systems, employee training on security best practices, and regular security assessments and audits.

Conclusion

In conclusion, network pivoting is a technique that allows attackers or security professionals to move laterally within a network, gaining access to additional systems and resources. It involves leveraging compromised systems as pivot points to facilitate unauthorized access. While network pivoting can be used maliciously, it is also employed by cybersecurity professionals for legitimate purposes such as testing network security and identifying vulnerabilities.

Throughout this article, we have explored various aspects of network pivoting. We discussed the concept of network pivoting, its goals, and the risks and challenges associated with it. We delved into two main categories of network pivoting techniques: port redirection and tunneling. Port redirection techniques involve redirecting network traffic to bypass security measures, while tunneling protocols create secure and encrypted tunnels for data transmission.

We also covered common tunneling protocols used in network pivoting, including SSH tunneling, SSL/TLS, IPsec, PPTP, and L2TP. Each protocol offers unique features and security capabilities for establishing secure tunnels and facilitating secure communication between systems or networks.

Furthermore, we explored network pivoting tools and techniques such as the Metasploit Framework, Cobalt Strike, proxychains, SSH tunneling, RDP Gateway, DNS tunneling, and IPv6 transition mechanisms. These tools and techniques can be utilized to facilitate network pivoting, either for malicious purposes or in the context of ethical hacking and security assessments.

However, it is essential to note that engaging in unauthorized network pivoting activities is illegal and unethical. Organizations and individuals should always obtain proper authorization and adhere to legal and ethical guidelines when conducting security testing or assessments.

In light of the risks and challenges associated with network pivoting, organizations should implement robust security measures to mitigate the potential impact. This includes implementing strong access controls, network segmentation, monitoring and detection systems, employee training on security best practices, and regular security assessments and audits.

Understanding network pivoting and its various techniques is crucial for both defenders and security professionals. By staying informed about the risks, challenges, and countermeasures associated with network pivoting, organizations can better protect their networks and systems from unauthorized access and potential security breaches.