xStack
®
DES-3810 Series Layer 3 Managed Ethernet Switch Web UI Reference Guide
439
How ARP Spoofing Attacks a Network
ARP spoofing, also known as ARP poisoning, is a method to attack an Ethernet network which may allow an attacker
to sniff data frames on a LAN, modify the traffic, or stop the traffic altogether (known as a Denial of Service – DoS
attack). The principle of ARP spoofing is to send the fake, or spoofed ARP messages to an Ethernet network.
Generally, the aim is to associate the attacker's or random MAC address with the IP address of another node (such as
the default gateway). Any traffic meant for that IP address would be mistakenly re-directed to the node specified by
the attacker.
Figure 10 – ARP Spoofing
The IP spoofing attack is caused by Gratuitous ARP that occurs when a host sends an ARP request to resolve its own
IP address. Figure 10 shows a hacker within a LAN to initiate ARP spoofing attack.
In the Gratuitous ARP packet, the “Sender protocol address” and “Target protocol address” are filled with the same
source IP address itself. The “Sender H/W Address” and “Target H/W address” are filled with the same source MAC
address itself. The destination MAC address is the Ethernet broadcast address (FF-FF-FF-FF-FF-FF). All nodes within
the network will immediately update their own ARP table in accordance with the sender’s MAC and IP address. The
format of a Gratuitous ARP packet is shown in Figure 11.
Figure 11 – Gratuitous ARP Packet
A common DoS attack today can be done by associating a nonexistent or any specified MAC address to the IP
address of the network’s default gateway. The malicious attacker only needs to broadcast one Gratuitous ARP to the
Summary of Contents for xStack DES-3810
Page 1: ......
