ARP poisoning, also known as ARP spoofing or ARP cache poisoning, is a network attack in which an attacker sends fake Address Resolution Protocol (ARP) messages to an Ethernet network. ARP is a protocol used to map an IP address (such as 192.168.1.1) to a physical machine address (such as a MAC address like 00:1a:2b:3c:4d:5e).
In a typical ARP poisoning attack, the attacker sends forged ARP messages to associate their own MAC address with the IP address of another device on the network. As a result, traffic intended for that IP address is sent to the attacker's MAC address. This allows the attacker to intercept, modify, or eavesdrop on the communication between two parties.
Here's a step-by-step explanation of how ARP poisoning works:
1. Normal ARP Operation:
- Device A wants to communicate with Device B.
- Device A sends an ARP request asking, "Who has the IP address of Device B?"
- Device B responds with its MAC address.
- Device A now has the correct MAC address for Device B and can communicate directly.
2. ARP Poisoning Attack:
- The attacker broadcasts fake ARP messages to the network, claiming to be Device B and providing the attacker's MAC address.
- Other devices on the network, including Device A, update their ARP caches with the forged information associating Device B's IP address with the attacker's MAC address.
3. Consequences:
- Traffic intended for Device B is now sent to the attacker's MAC address.
- The attacker can intercept, modify, or analyze the communication between Device A and Device B.
ARP poisoning can be used for various malicious purposes, including:
- Packet Sniffing: The attacker can capture sensitive information passing between two parties.
- Man-in-the-Middle Attacks: The attacker can modify or inject malicious content into the communication.
- Denial of Service: By disrupting normal network communication.
To mitigate ARP poisoning attacks, network administrators can implement various security measures such as ARP spoofing detection tools, static ARP table entries, or network encryption methods. Additionally, using protocols like DHCP Snooping and dynamic ARP inspection can enhance network security. Regularly monitoring network traffic for suspicious activities is also crucial for identifying and responding to ARP poisoning attacks.
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