DHCP Spoofing is a type of cyber attack where an attacker sets up a rogue DHCP server on a network. This rogue server responds to DHCP requests from clients, providing malicious configurations. By doing so, the attacker can manipulate network traffic, often redirecting it through their own machine.

The primary goal of DHCP Spoofing is to intercept and control the communication between devices and the legitimate DHCP server. This can lead to various malicious activities, such as intercepting sensitive data or disrupting network services. The attack exploits the lack of authentication in the DHCP protocol, making it a significant threat in network security.

How does DHCP Spoofing Work?

DHCP Spoofing works by exploiting the DHCP protocol's lack of authentication. An attacker sets up a rogue DHCP server on the network, which then responds to DHCP requests from clients. When a client sends a DHCPDISCOVER message to find available DHCP servers, the rogue server intercepts this request and responds with a DHCPOFFER message, providing malicious network configurations.

The rogue DHCP server can list itself as the default gateway or DNS server in its response. This allows the attacker to redirect network traffic through their machine, enabling them to intercept and analyze the data. The attacker can also perform a Denial of Service (DoS) attack by flooding the legitimate DHCP server with requests, exhausting its IP address pool and preventing it from serving legitimate clients.

By manipulating DHCP messages, the attacker gains control over the network traffic, often setting up a man-in-the-middle scenario. This manipulation disrupts the normal communication flow, making it easier for the attacker to carry out further malicious activities.

What are Examples of DHCP Spoofing?

Examples of DHCP spoofing can be seen in various attack scenarios. One common method is the DHCP Starvation Attack, where an attacker sends numerous DHCPREQUEST messages with spoofed MAC addresses. This depletes the DHCP server's pool of available IP addresses, preventing it from responding to legitimate requests. Following this, the attacker can set up a rogue DHCP server to respond to new DHCP requests with malicious configurations.

Another example is the Man-In-The-Middle (MITM) Attack. Here, the attacker combines DHCP Starvation and Rogue DHCP attacks to intercept and manipulate network traffic. By setting themselves as the DNS server and default gateway, the attacker can redirect DNS requests, leading to credential harvesting and forced authentication scenarios. These examples highlight the diverse tactics attackers use to exploit DHCP vulnerabilities.

What are the Potential Risks of DHCP Spoofing?

Understanding the potential risks of DHCP Spoofing is crucial for maintaining network security. Here are some of the key risks associated with this type of attack:

• Data Interception: Attackers can intercept sensitive data by positioning themselves as the default gateway or DNS server, allowing them to monitor and manipulate network traffic.

• Unauthorized Network Access: Rogue DHCP servers can provide incorrect network configurations, granting attackers unauthorized access to network resources and sensitive information.

• Network Disruption: DHCP Starvation attacks can deplete the DHCP server's pool of IP addresses, preventing legitimate devices from connecting to the network and causing significant disruption.

• Credential Theft: By forcing authentication and harvesting credentials, attackers can obtain sensitive information such as NetNTLM hashes, leading to further security breaches.

• Increased Risk of Further Attacks: Once attackers control network traffic, they can launch additional attacks, such as Man-In-The-Middle (MITM) attacks, to further compromise network security.

How can you Protect Against DHCP Spoofing?

Protecting against DHCP Spoofing requires a combination of network security measures. Here are some effective strategies:

• Enable DHCP Snooping: Configure DHCP snooping on network switches to monitor and control DHCP traffic, ensuring only trusted ports can send DHCP offers.

• Implement Port Security: Bind the DHCP server's MAC address to a specific port and limit the number of MAC addresses allowed on that port to prevent unauthorized devices from connecting.

• Use VLAN Segmentation: Enable DHCP snooping for specific VLANs to isolate and control DHCP traffic within those segments.

• Deploy IP Source Guard: Use IP Source Guard in conjunction with DHCP snooping to filter traffic based on IP-MAC address bindings, preventing IP address spoofing.

• Conduct Regular Penetration Tests: Perform automated penetration tests to identify and address vulnerabilities to DHCP spoofing attacks.