ARP Spoofing

ARP Spoofing, also known as ARP Poisoning, is a type of cyberattack in which an attacker sends falsified Address Resolution Protocol (ARP) messages over a local network. This technique allows the attacker to associate their MAC address with the IP address of another device, such as a gateway or server, enabling them to intercept, modify, or block data intended for that address.

The ARP protocol is fundamental to local area networks (LANs) and is used to map IP addresses to MAC addresses. However, ARP lacks authentication, making it vulnerable to spoofing. Once an attacker is able to spoof ARP replies, they can effectively redirect traffic through their own device—a classic man-in-the-middle (MITM) attack scenario.

Variants

There are several ways ARP spoofing can be used to compromise a network:

• Man-in-the-Middle (MITM) Attacks: The attacker intercepts communications between two devices, often without either party realizing. Sensitive data like login credentials can be captured.
• Session Hijacking: By spoofing ARP responses, attackers can steal authenticated sessions and impersonate legitimate users.
• Denial of Service (DoS): The attacker can associate an IP address with a non-existent MAC address, effectively blocking traffic to that address.

Types

Targeted ARP Spoofing

• Gateway Spoofing: The attacker targets the gateway device, positioning themselves between all traffic going from internal devices to the outside network.
• Client Spoofing: The attacker impersonates a specific client machine, potentially redirecting data meant for that user to themselves.

Widespread ARP Poisoning

• Broadcast Poisoning: The attacker sends forged ARP replies to many devices on the network at once, affecting broader communications.

Impact

The impact of ARP spoofing can be severe. Attackers may gain access to unencrypted sensitive data, compromise user credentials, and disrupt communications across a network. In enterprise environments, this can lead to data breaches, financial loss, and reputational damage. In some cases, attackers may even use ARP spoofing as a stepping stone for more complex network intrusions or malware distribution.

Discoverability

Detecting ARP spoofing can be challenging due to its silent nature. However, signs such as duplicate IP addresses, unexpected packet flows, and sudden network slowness may indicate its presence. Network administrators can use tools like ARPWatch, XArp, or Wireshark to monitor ARP traffic and identify anomalies. Regular monitoring and alerting on MAC-IP pair inconsistencies can aid in early detection.

Protection

• Use static ARP entries for critical devices to prevent spoofing.
• Enable dynamic ARP inspection (DAI) on switches to validate ARP packets.
• Segment networks using VLANs to reduce exposure to local ARP attacks.
• Employ packet filtering and intrusion detection/prevention systems (IDS/IPS).
• Use encrypted communication protocols like HTTPS, SSH, and VPNs to safeguard data even if intercepted.