What Is ARP Poisoning?

ARP (Address Resolution Protocol) poisoning is a cyberattack technique that exploits the ARP cache within a local network to intercept, alter, and eavesdrop on traffic. As ARP is a mechanism that enables network communications to reach specific devices on a network, threat actors can manipulate and send false ARP messages. Once an ARP cache is poisoned, it can be leveraged for various malicious activities, such as capturing sensitive information, stealing data, and launching additional attacks.

How ARP Poisoning Works 

Address Resolution Protocol is a process that facilitates communication between devices on a local network by linking IP addresses to Media Access Control (MAC) addresses—unique hardware identifiers assigned to every device. Devices on a network use ARP to find MAC addresses associated with IP addresses to facilitate proper data delivery. Once an IP-to-MAC connection is established, information is stored in an ARP cache, so repeat ARP requests are unnecessary. 

ARP Poisoning Steps

1. Spoofing

To perform an ARP poisoning attack, threat actors send forged messages to targeted devices, which include the threat actor’s MAC address and the IP address of the target system or user. The spoofed messages claim the threat actor’s MAC address corresponds to the IP address of the target device, allowing the threat actor to receive all communications intended for the legitimate system.

2. Caching

The ARP cache on the target device is updated with the forged information, falsely associating an IP address with the threat actor’s MAC address. The ARP cache stores this information, giving threat actors persistent access.

3. Intercept

The target device sends network traffic to the threat actor’s MAC address. This enables threat actors to intercept and modify data for malicious activities.

Types of ARP Poisoning Attacks

Man-in-the-Middle (MiTM) Attack

MiTM attacks occur when threat actors insert themselves into conversations between two users or applications. In this ARP poisoning attack, compromised systems redirect network traffic to the threat actor, who leverages their position to insert malware and steal sensitive data.

Distributed Denial of Service (DDoS) Attack

DDoS attacks are an attempt to prevent users from accessing network resources. Rather than intercepting traffic, ARP DDoS attacks flood networks with many spoofed ARP packets to overwhelm a device’s ARP cache and cause network disruption.

Session Hijacking

Session hijacking occurs when a threat actor steals a web cookie to impersonate a target user. This attack could be used to gain control over a specific user’s web applications.

ARP Poisoning vs. ARP Spoofing

While ARP spoofing and ARP poisoning are often used interchangeably, they have slightly different meanings. ARP spoofing is a broader term for sending forged ARP messages to falsely associate a malicious MAC address with a legitimate IP address. ARP poisoning is a more specific type of ARP spoofing that poisons the ARP cache of targeted devices on a network to intercept and manipulate traffic. 

How to Detect and Prevent ARP Poisoning

Prevent ARP poisoning attacks with the following cybersecurity solutions:

Static ARP Entries

Manually configuring static ARP entries ensures that IP-to-MAC connections are fixed and resistant to changes caused by ARP poisoning attacks. Rather than relying on dynamic ARP, in which devices automatically update their ARP cache, this ensures that all attempted changes must be reviewed.

Endpoint Security

Endpoint security involves implementing security measures on individual devices to detect and block malicious activity such as ARP poisoning. By securing endpoints, organizations can fortify their network against potential threats and prevent threat actors from breaching systems via individual devices.

Zero Trust Network Access (ZTNA)

ZTNA is a security model that operates on the assumption that all network connections pose a potential threat to security. It requires users to continuously validate their identity to view any resources or data within the system, mitigating unauthorized access.

Secure Network Protocols

Organizations can prevent ARP poisoning attacks by using protocols like HTTPS and SSH. This ensures sensitive communication and data are encrypted in transit, helping to prevent threat actors from eavesdropping on network traffic. 

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