VLAN hopping
VLAN Hopping Definition
VLAN hopping is a security exploit in computer networking that allows an attacker to bypass the intended limitations of virtual local area networks (VLANs). It is a technique used by hackers to gain unauthorized access to network resources by manipulating VLAN configurations and taking advantage of vulnerabilities in switches.
How VLAN Hopping Works
VLAN hopping attacks exploit various vulnerabilities in network switches and the way VLANs are configured. Here are some common methods used in VLAN hopping:
Double Tagging: In this technique, the attacker sends a frame with two 802.1Q tags. The first tag is the attacker's own VLAN tag, and the second tag is the VLAN tag of the target VLAN. By doing so, the attacker tricks the switch into forwarding the frame to the unintended VLAN.
Switch Spoofing: Switch spoofing is another method used in VLAN hopping attacks. The attacker gains access to the management VLAN by spoofing switch advertisements. This allows the attacker to intercept and modify network traffic, potentially gaining unauthorized access to sensitive information.
Dynamic Trunking Protocol (DTP) Exploitation: DTP is a Cisco proprietary protocol used to negotiate trunk links between switches. By exploiting DTP, an attacker can convince a switch to change its operational mode to trunking. This gives the attacker access to multiple VLANs, bypassing the intended VLAN restrictions.
Prevention Tips
To prevent VLAN hopping attacks and enhance the security of your network, consider implementing the following measures:
Disable Unused Ports: Disable any unused switch ports to prevent an attacker from gaining physical access to the network through these ports. By disabling unused ports, you reduce the attack surface and limit potential entry points.
Disable Dynamic Trunking Protocol (DTP): Manually configure switch ports to be access ports rather than trunk ports, and disable DTP. By doing so, you eliminate the risk of DTP exploitation, which is commonly used in VLAN hopping attacks.
Implement VLAN Access Control Lists (VACLs): VACLs provide an additional layer of security by allowing you to control traffic flow between VLANs. By enforcing stricter access control rules, you can prevent unauthorized communication between VLANs and reduce the risk of VLAN hopping.
Enable Port Security: Port security allows you to restrict the number of MAC addresses allowed on a particular switch port. By configuring port security, you can prevent unauthorized devices from connecting to the network and limit the potential impact of VLAN hopping attacks.
Regularly Update Switch Firmware: Keep your network switches up to date with the latest firmware and security patches. This ensures that any known vulnerabilities that could be exploited for VLAN hopping are patched and mitigated.
It is important to note that prevention techniques may vary depending on the specific network infrastructure and switch vendor.
Related Terms
Network Segmentation: Network segmentation is the practice of dividing a computer network into smaller, isolated networks for security purposes. It helps to reduce the attack surface and contain the impact of security breaches.
802.1Q Tag: The 802.1Q tag is an IEEE standard for VLAN tagging in Ethernet networks. It allows network administrators to assign VLAN membership to Ethernet frames, enabling the creation of isolated VLANs within a single physical network.