ARP Address Resolution Protocol (ARP) spoofing is a protocol used to convert Internet Protocol (IP) addresses to media access control (MAC) addresses. All devices on the network that can communicate with one another will send out ARP queries to discover each other’s media access control (MAC) addresses.
Spoofing attacks, like Address Resolution Protocol (ARP) spoofing and ARP poisoning, are used by hackers to steal information. The goal of an ARP spoofing attack is to trick a device into sending communications to the hacker instead of the intended recipient.
This gives the hacker access to everything you say while using your device, including sensitive information like passwords and credit card details. You can protect yourself from such attacks in a number of different ways.
The ARP Protocol: What Is It?
Using ARP, network messages can be directed to a specific node in a network. ARP is a protocol that translates between Media Access Control (MAC) and IP addresses. ARP is commonly used by devices to make contact with the gateway or router that provides them with Internet access.
Hosts are able to communicate with other hosts and devices on a network because they maintain a mapping table between IP addresses and MAC addresses. If the host cannot determine the MAC address for a given IP address, it will send out an ARP request packet to other devices on the network to discover the corresponding MAC address.
Since the ARP protocol was not developed with security in mind, it does not verify that a reply to an ARP request comes from a trusted source. It also allows hosts to get ARP replies even if they’ve never asked for them. The ARP protocol is susceptible to spoofing attacks because of this flaw.
The antiquated IPv4 standard’s 32-bit IP addresses are the only ones that work with ARP. The newer IPv6 protocol makes use of a separate protocol called Neighbor Discovery Mechanism (NDP), which is secure because it uses cryptographic keys to verify host identities. Although the majority of the Internet has moved on from the antiquated IPv4 protocol, ARP is still in widespread use.
Definition of ARP Spoofing
Malicious ARP spoofing, also known as ARP poisoning, occurs when malicious ARP packets are delivered to a LAN’s default gateway. As a result, the ARP table’s IP/MAC address pairings are updated.
A hacker can target a specific IP address by telling the gateway to associate a specific MAC address with that IP. Additionally, the attacker’s IP address can be linked to the victim’s MAC address.
The default gateway then propagates the updated IP/MAC mappings to all other devices on the network and stores them in its own cache. This means any subsequent communications will be routed to the attacker’s system instead of their intended destination.
ARP poisoning is the practice of manipulating the MAC addresses assigned to IP addresses on other networked devices by exploiting ARP’s vulnerabilities. It should be noted that the developers of ARP in 1982 did not prioritize security, and thus did not implement any methods for authenticating ARP messages. Every node in the network can answer an ARP request, regardless of who the original message was intended for.
If Computer A “asks” Computer B for its MAC address, an attacker on Computer C could respond on behalf of Computer B, and Computer A would mistake the attacker’s response for one from Computer B. This oversight has allowed for multiple attacks. Any malicious actor with access to common tools can “poison” the ARP caches of other hosts on a local network by flooding them with bogus entries.
ARP spoofing attacks are advantageous to hackers because it can be difficult for their targets to realize that their traffic is being impacted (although there are ways to detect and prevent ARP spoofing attacks, as we’ll see in a moment).
Can you explain how ARP poisoning/spoofing works?
An attacker using an ARP cache poisoning attack will attempt to inject false information into local area network traffic in order to reroute connections to their device. If the attack is successful, all future connections to that IP address will be routed through the attacker’s controlled device, as the connection initiator will rely on the false data it finds in the cache.
Storing a spoofed address in the ARP cache, or “poisoning,” is one form of ARP spoofing, while using a spoofed address in ARP messages, or “spoofing,” is another. They are two separate ideas that are often discussed together because they refer to the same set of circumstances.
In what ways can you shield your network from ARP poisoning attacks?
It is possible to defend against ARP Poisoning attacks in a number of ways:
Each MAC address on a network can be assigned to a specific IP address using a static ARP table. This requires a lot more work from the admins behind the scenes, but it protects against ARP Poisoning attacks very well.
Since static ARP tables require manual updates to the ARP tables on all hosts whenever the network changes, they are impractical for most large businesses. When security is paramount, however, isolating a network subnetwork where static ARP tables are used can help to protect particularly delicate information.
Protecting the Switch:
Most managed Ethernet switches prevent attacks by blocking ARP Poisoning. These features, which are sometimes called Dynamic ARP Inspection (DAI), examine each ARP message for potential threats and delete them if they are found to be invalid. Often, DAI can be configured to limit the rate at which ARP messages can travel through the switch, further preventing DoS attacks.
DAI and similar technologies were once reserved for high-end networking equipment, but are now standard on virtually all business-grade switches, including those used by smaller businesses.
Most networking professionals agree that DAI should be enabled on all ports except those connected to other switches. The feature has no discernible impact on performance, but it may need to be activated in tandem with others, such as DHCP Snooping.
The strength of an ARP Cache Poisoning attack can be mitigated by increasing the switch’s port security setting. Port security helps prevent an attacker from spoofing multiple network identities by limiting the number of MAC addresses that can be assigned to a switch port.
Covering your body in armor:
Your business might be safer from ARP Poisoning attacks if you take precautions to limit who can enter and leave your building. Because ARP messages are not routed outside of the local network, any potential attackers must be either physically close to the target network or already in control of a computer on the network.
Since a wireless network’s signal may be sufficient if it reaches a street or parking lot, proximity does not always imply that the attacker must be in close proximity to the network itself. Connectivity to any wired or wireless network can be restricted to only approved and/or managed devices with the help of protocols like 802.1x.
Complete segregation of networks:
As was mentioned before, ARP messages never leave the local subnet. A well-segmented network may be less susceptible to ARP cache poisoning because an attack in one subnet cannot affect devices in another. Concentrating critical resources in a separate, better-protected part of the network can significantly lessen the damage that could be done by an ARP Poisoning attack.
Encryption won’t prevent an ARP attack, but it can mitigate its effects if one occurs. Login credentials were often sent in plain text, making them easy prey for man-in-the-middle attacks.
With more websites adopting SSL/TLS encryption, hacks like these are becoming increasingly difficult to pull off. The threat actor can still intercept the traffic because it is encrypted, but it will be useless to them.