What is the ARP Protocol?

The Address Resolution Protocol (ARP) is a protocol employed for mapping IPv4 addresses to the physical (MAC) address that resides in a Local Area Network (LAN).

As a protocol that functions at the Link Layer (layer 2 of the OSI model), ARP is crucial in facilitating communication between two devices belonging to the same broadcast domain.

For instance, when a device requires forwarding information to another device on the same LAN but does not know the other device’s MAC address, ARP comes in handy by converting this address into the device’s MAC address to ensure the data packets are delivered correctly.

Also Read: What is DNS Poisoning or DNS Spoofing?

ARP has a method that sends out requests and receives replies. ARP requests are used similarly when a device needs to discover the MAC address of another device on the network.

The other device with the corresponding IP address sends an ARP reply containing its MAC address. This information is then placed in the ARP table of the requesting device to make future interaction faster in case interaction is needed again.

ARP is one of the most essential protocols because it helps to organize the adequate and accurate flow of data inside a local network using IP addresses to provide hardware addresses.

What is ARP Spoofing or ARP Poisoning?

ARP Spoofing, also known as ARP Poisoning, is a type of cyber attack that involves sending falsified Address Resolution Protocol messages over the local area network.

This attack links the MAC address of the attacker with the IP address of a genuine computer or server on the network.

In this way, the attacker successfully gains control over the data, which may either be transmitted, altered, or even prevented from reaching the rightful intended recipient.

This kind of attack takes advantage of how ARP functions, as there are no open connectivity checks to confirm ARP messages’ validity.

In this attack, once the attacker has ensured that their MAC address is associated with a legitimate IP address, the attacker can perform any of the following activities:

They can also compromise data through stealing usernames and passwords or other types of private data or perform man-in-the-middle attacks to intercept traffic, change traffic to malicious websites, or interrupt provided services.

ARP Spoofing is most dangerous because it can be easily performed by anybody with any regular Laptop using simple software, and its consequences are highly damaging for personal and business use since it leads to data leakage and huge losses.

How to Detect an ARP Cache Poisoning Attack?

ARP cache poisoning attacks can be challenging to detect due to their stealthy nature. However, by using a combination of network monitoring tools, logging, and vigilance, network administrators can identify signs of an attack.

Here are several methods to detect ARP cache poisoning:

Software tools that can be used to investigate ARP cache poisoning attacks include Wireshark and ARPwatch.

Administrators can use Wireshark’s packet analyzer to capture and review ARP packets on the network; thus, they can find ARP traffic with duplicated IPs, or ARP replies that look suspicious and are signs of ARP spoofing.

ARPwatch listens to ARP traffic and logs the IP-MAC address mapping, notifying the administrator whenever it is discovered that the MAC address of an IP address has been changed; this is another way of checking for ARP spoofing.

Also Read: What is DNS Poisoning or DNS Spoofing?

Unusual Network Traffic Patterns

Suspicion of ARP spoofing can be observed through scanning for strange network traffic in the network. Because ARP poisoning results in the redirection of traffic via the attacker’s machine, constant high latency, and unnatural traffic patterns are observed.

Another indication that an ARP spoofing attack may be in process or may have been recently executed is when the connections are frequently lost, the speeds are reduced, or there are instances of intermittent connectivity.

This implies that administrators can identify early signs of such areas by monitoring these factors.

ARP Table Inspection

Another method is the periodic screening of ARP tables on essential devices. Usually, administrators can cross-check discrepancies, including where multiple IP addresses are resolved to a single MAC address or many MAC addresses to one IP address.

Also, it is possible to employ scripts for the automatic scanning of ARP tables and identifying the differences in the tables, thus allowing the revelation of malicious activity.

Dynamic ARP Inspection (DAI)

One ARP spoofing by enabling the Dynamic ARP Inspection (DAI) on the managed switches. DAI filters ARP packets, checks the packet list for the ARP IP-to-MAC list contained within the DAI component, and reports ARP spoofing attempts to network administrators.

This makes them take an extra measure of protecting the network than that adopted by traditional methods.

Comparing ARP Entries Across Devices

By analyzing the content of ARP tables of two devices belonging to the same switch, specific disparities will be noticed due to ARP poisoning.

After cross-checking ARP entries, the administrators know of disparities likely to indicate that an attacker is mimicking ARP responses, hence giving a quick follow-up.

Also Read: What is Email Spoofing? Example & Prevention

ARP attack protection is crucial for maintaining network security. Implementing a combination of proactive measures and security protocols can significantly reduce the risk of ARP cache poisoning.

Here are several strategies to prevent ARP spoofing:

Static ARP Entries

Static ARP is one of the most effective ways of securing the network against ARP spoofing attacks, such as manually assigning ARP entries for critical devices.

One must configure static mappings between an IP address and the MAC address of the most essential devices so that fake ARP packets cannot alter ARP entries. This approach best suits small networks, as adding new static entries requires administrative action.

Dynamic ARP Inspection (DAI)

One of the protective measures of ARP spoofing includes using or activating DAI on the network switches.

This entails checking for ARP packets on the network and the authenticity of these packets against the database of legitimate, authorized IP-to-MAC address pairings; the DAI also filters out any ARP packets that are malicious or spoofed.

It makes it proactive in a sense and filters only legitimate ARP traffic while denying any attacker tampering with ARP tables.

Port Security

If enabled on network switches, port security can restrict the maximum number of MAC addresses learned over a port.

As each port is limited to a particular number of MAC addresses, the attacker cannot insert other unwanted devices that may engage in ARP spoofing.

Another type of port security is available that can make the port too close or notify the administrator when a violation is encountered.

This is where the ARP spoofing detection tools like ARPwatch, XArp, or even Wireshark come in handy because they can be used to check the ARP traffic for any malicious activities.

These tools are designed to notify administrators when there is a possibility of an ARP spoofing attack taking place so that the threat can be dealt with.

 Based on the evidence collected, continuous monitoring and analysis of ARP traffic can effectively identify and deter ARP spoofing.

Network Segmentation

Implementing segmentation where the network is divided into smaller subnets or virtual Local Area Networks (VLANs) can help minimize ARP spoofing attacks.

Suppose the administrators place essential systems or particular information in one or more distinct network domains.

In that case, it will prove harder for an attacker to remain undetected and navigate the network. It is also important to note that network segmentation makes the management process of static ARP entries and DAI configurations easier.

Conclusion

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