What is ARP poisoning and how can it be mitigated?

ARP (Address Resolution Protocol) poisoning, also known as ARP spoofing, is a network attack in which an attacker sends falsified ARP messages over a local area network. The goal of ARP poisoning is to associate the attacker's MAC address with the IP address of another host (such as the default gateway), diverting traffic intended for that IP address to the attacker's machine. This can lead to various malicious activities, including man-in-the-middle attacks, interception of sensitive information, and network disruption.

Here's a technical explanation of ARP poisoning and methods to mitigate it:

ARP Protocol Overview:

1. Address Resolution Protocol (ARP):
   • ARP is used to map an IP address to a MAC address within a local network.
   • When a device wants to communicate with another device on the same subnet, it uses ARP to discover the MAC address associated with the target's IP address.

ARP Poisoning Attack:

1. Spoofing ARP Replies:
   • The attacker sends ARP reply messages with a falsified MAC address, claiming to be the legitimate owner of a particular IP address.
   • These ARP replies are cached by other devices on the network, associating the attacker's MAC address with the target IP address.
2. Man-in-the-Middle (MITM):
   • The attacker can position themselves as a man-in-the-middle, intercepting and potentially modifying the communication between two legitimate parties.

Mitigation Techniques:

1. Static ARP Entries:
   • Manually configure static ARP entries on critical devices, specifying the correct IP-to-MAC address mappings.
   • This helps prevent ARP poisoning attacks by enforcing a fixed mapping.
2. ARP Spoofing Detection Tools:
   • Use specialized tools or intrusion detection systems that can detect abnormal ARP behavior.
   • These tools can identify discrepancies between the IP-MAC mappings in ARP replies and those in the ARP cache.
3. Port Security:
   • Implement port security features on network switches to restrict the number of MAC addresses allowed on a port.
   • This prevents an attacker from connecting multiple devices to a single switch port and attempting ARP poisoning.
4. Network Segmentation:
   • Divide the network into segments using VLANs (Virtual Local Area Networks).
   • This limits the scope of ARP poisoning attacks, as an attacker's influence is confined to the VLAN they are in.
5. Use ARP Spoofing Prevention Software:
   • Deploy software solutions that actively monitor ARP traffic and can detect and prevent ARP spoofing attacks.
6. Encryption and Authentication:
   • Use encrypted protocols (such as HTTPS) and strong authentication mechanisms.
   • This helps protect sensitive data even if a man-in-the-middle attacker intercepts the communication.
7. Implement ARP Spoofing Detection on Hosts:
   • Some operating systems and security software offer features to detect and mitigate ARP spoofing at the host level.
8. Network Monitoring:
   • Regularly monitor network traffic and look for unusual patterns or discrepancies in ARP traffic.