Introduction to DHCP and Its Role in the Network
Before diving into the details of attacks on DHCP servers, let's explain what a DHCP server is and what role it plays in a computer network.
What is a DHCP Server?
Every device on a network – whether it's a computer, notebook, phone, or tablet – needs certain parameters to communicate properly on the network, such as an IP address, default gateway IP address, DNS server address, and subnet mask.
A network administrator has two options for assigning these parameters to devices:
Static Addressing: The administrator manually sets the parameters for each device. This solution offers complete control over the network, but it is labor-intensive and difficult to maintain, especially when adding new devices.
Dynamic Allocation Using a DHCP Server: The DHCP server automatically assigns the necessary parameters. This significantly simplifies network management and the addition of new devices.
How Does DHCP Work?
When you connect a device to the network, the following process occurs:
- DHCP Discover: The device sends a query to all network elements to find a DHCP server.
- DHCP Offer: The DHCP server responds with an offer of configuration (IP address, DNS, default gateway, subnet mask).
- DHCP Request: The device requests the allocation of this configuration.
- DHCP Acknowledgement: The DHCP server confirms the allocation of the configuration.
DHCP Spoofing
DHCP spoofing is an attack in which the attacker masquerades as a DHCP server. The attacker listens to network traffic and responds to DHCP Discover queries before the legitimate DHCP server. If the device accepts the fake offer, all communication is routed through the attacker, who can eavesdrop on data and spoof server responses.
Defense Against DHCP Spoofing
Effective defense against DHCP spoofing requires:
- Router Configuration: Set which ports the DHCP server operates on so the router can filter out fake DHCP Offer responses.
- Database of DHCP Transactions: Create a database of successful DHCP transactions to help identify suspicious activities on the network.
Conclusion
Do you want to ensure that your network is secure and resilient against attacks? Need help developing web or mobile applications with a focus on IT security? Contact us, and we’ll be happy to assist you!
