A Gentle Introduction to ARP Spoofing

Address Resolution Protocol (ARP) is a stateless mechanism called to translate IP addresses into machine MAC addresses. To determine the MAC addresses of other machines, all network devices that require network communication broadcast ARP queries throughout the system.

 

Hackers utilize spoofing attacks such as Address Resolution Protocol (ARP) spoofing or ARP poisoning to intercept data. By fooling a device into sending messages to the hacker instead of the intended recipient, a hacker can carry out an ARP spoofing attack. 

 

The hacker then has access to any conversations on your device, including private information like passwords and credit card numbers. Fortunately, there are several methods you may defend yourself against these assaults.

 

Also Read | What is Spoofing?

 

 

What is the ARP Protocol?

 

ARP is a protocol that makes it possible for network messages to get to a particular network device. ARP converts Media Access Control (MAC) addresses into Internet Protocol (IP) addresses and the other way around. Devices typically utilize ARP to get in touch with the router or gateway that gives them access to the Internet.

 

A mapping table between IP addresses and MAC addresses is kept by hosts and is used by them to connect to other hosts and devices on the network. The host will send out an ARP request packet to other devices in the network to find the corresponding MAC address if it is unable to determine the MAC address for a specific IP address.

 

The ARP protocol does not confirm that a response to an ARP request originates from an authorized party because it was not created with security in mind. Additionally, it enables hosts to receive ARP answers even though they have never made a request. The ARP protocol has a flaw in this area, which makes it vulnerable to spoofing attacks.

 

Only 32-bit IP addresses in the dated IPv4 standard are compatible with ARP. Neighbor Discovery Mechanism (NDP), a distinct protocol used by the more recent IPv6 protocol, is safe and employs cryptographic keys to confirm host identities. ARP is still widely used, although the majority of the Internet still employs the outdated IPv4 protocol.

 

Also Read | Difference between Phishing and Spoofing

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How does ARP Spoofing work?

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ARP Spoofing: What is it?

 

When malicious ARP packets are delivered to a LAN's default gateway, the phenomenon known as ARP spoofing, often referred to as ARP poisoning, takes place. The IP/MAC address pairings in the ARP table are changed as a result. 

 

The hacker instructs the gateway that their MAC address should now be connected to the IP address of the intended victim. The opposite also happens, with the IP address of the attacker being associated with the MAC address of the target.

 

The new IP/MAC relationships are then sent to the other network nodes by the default gateway, who caches them. This indicates that the attacker's system will receive all following communications rather than the intended recipient. 

 

Utilizing ARP's flaws to tamper with other networked devices' MAC-to-IP mappings is known as ARP poisoning. When ARP was first developed in 1982, security was not a top priority, hence the protocol's creators did not include any techniques for authenticating ARP messages. No matter who the initial communication was meant for, every device on the network is capable of responding to an ARP request.

 

 For instance, if Computer A "asks" for Computer B's MAC address, Computer C may return with an attacker's response, and Computer A would regard this response as genuine. Several attacks have been made possible by this omission. A threat actor can "poison" the ARP cache of other hosts on a local network by using readily available tools to load the ARP cache with false entries.

 

The fact that ARP spoofing attacks happen at a low level is advantageous to the hackers because it may be challenging for the targets to recognize that their traffic is being impacted (although, as we'll see momentarily, there are ways to both detect and prevent ARP spoofing attacks).

 

Also Read | Proxy Firewall: An Enhanced Level of Security

 

 

How does ARP poisoning/spoofing operate?

 

To reroute connections to their device, an attacker performing an ARP cache poisoning attack tries to inject bogus information into local area network traffic. If the attacker is successful, subsequent connections to a particular IP address will go through a device under the control of the attacker since the connection initiator will use the bogus information it finds in the cache to connect.

 

ARP poisoning refers to storing a bogus address in the ARP cache, while ARP spoofing refers to utilizing a fake address in ARP messages. Although they pertain to the same series of events and are two distinct concepts, they are frequently discussed together.

 

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Where do ARP poisoning attacks happen?

 

There is no chance that an ARP spoofing attack would originate from outside the present network because ARP information is never routed outside the local subnet. Only if the attackers have a way to access the same local network as the victim's machine are these attacks dangerous.

 

Since ARP is utilized in both Ethernet and Wi-Fi networks, Wi-Fi hotspots can be a good place to start an attack. ARP packets can be sent to a hotspot's network as long as the attacker can connect to it (and log in like any other user). This is one reason to exercise extra caution when utilizing public Wi-Fi networks with your mobile devices and to avoid creating un-secure (plain-text) connections at all costs.

 

Also Read | Cyber Security Awareness: Ways to Protect Cyber Attack Vulnerability

 

 

What ARP Spoofing Is Used For?

 

The fact that ARP spoofing is frequently used as a jumping-off point for other, more complex types of assaults plays a significant role in why it is so deadly. Once an attacker has executed an ARP spoofing attack successfully, they can then quickly switch to:

 

• DDoS attacks: 

 

The attacker can initiate a DDoS attack by using the address of the server they wish to target rather than their own MAC address. This can be done repeatedly for a lot of different IP addresses to saturate the victim with traffic.

 

 

• Session hijacking: 

 

Using ARP spoofing, the hacker can obtain your session ID and use it to log into the victim's accounts.

 

 

• Continued packet theft:

 

The attacker needn't take any additional action. They can continue sniffing your packets and stealing your data (which is why, as we'll discuss later, using TLS and HTTPS to secure your conversations is so crucial).

 

 

• Communication alterations: 

 

In essence, this would be a man-in-the-middle attack. The hacker can push harmful files or websites to the victim's computer by intercepting and altering traffic.

 

Also Read: What is a Man-in-the-Middle Attack?

 

• ‍MiTM: 

 

The most common and destructive application of MiTM attacks is this one. The hacker will utilize phony ARP answers to execute this attack. The compromised IP often serves as the subnet's default gateway. The targeted system will begin communicating with the attacker's device's MAC address as soon as the phony ARP response is transmitted.

 

The target device will then begin incorrectly passing the information and traffic to the attacker's machine, treating it as a network channel. Few attackers even employ tools like Ettercap to carry out this attack, which allows them to pass as a proxy or read the altered data that is intended to be transmitted to the targeted destination.

 

Also Read | What is a Firewall? Types of Firewall

 

 

How to Prevent ARP Poisoning Attacks?

 

There are several ways to stop ARP Poisoning attacks:

 

• Static ARP Tables: 

 

All of the MAC addresses in a network can be statically mapped to their correct IP addresses. This adds a significant administrative effort but is incredibly effective at preventing ARP Poisoning attacks. 

 

Static ARP tables are impracticable for most bigger businesses because they need manual updates of the ARP tables on all hosts whenever the network changes. However, separating a network segment when static ARP tables are utilized can help to safeguard sensitive data in circumstances where security is essential.

 

 

• Switch Security: 

 

The majority of managed Ethernet switches have protections against ARP Poisoning attacks. These capabilities, which are sometimes referred to as Dynamic ARP Inspection (DAI), assess the legitimacy of each ARP message and discard any that seem questionable or malicious. To successfully stop DoS attacks, DAI can also often be set up to restrict the speed at which ARP messages can transit through the switch.

 

Formerly reserved for high-end networking equipment, DAI, and comparable technologies are now present on practically all business-grade switches, including those used in smaller enterprises. 

 

Enabling DAI on all ports other than those that are linked to other switches is typically regarded as best practice. Although there is no noticeable performance hit from the feature, it might need to be activated alongside other features like DHCP Snooping.

 

A switch's port security setting can also lessen the impact of ARP Cache Poisoning attacks. By restricting the number of MAC addresses that can be assigned to a switch port, port security can prevent an attacker from maliciously assuming several network identities.

 

 

• Physical Protection: 

 

Keeping physical access to your place of business properly controlled might lessen the impact of ARP Poisoning assaults. Potential attackers must be nearby the target network physically or already be in charge of a computer on the network because ARP messages are not routed outside of the local network. 

 

A signal that reaches a street or parking lot may be adequate in the case of wireless networks, therefore proximity does not always imply that the attacker needs direct physical contact. The usage of technologies like 802.1x can make sure that only vetted and/or managed devices can connect to the network, whether it is wired or wireless.

 

 

• Network Isolation: 

 

ARP messages, as previously mentioned, don't leave the local subnet. Because an attack in one subnet cannot affect devices in another, a well-segmented network may be generally less vulnerable to ARP cache poisoning. The potential impact of an ARP Poisoning attack can be significantly reduced by concentrating crucial resources in a dedicated network segment with improved protection.

 

 

• Encryption: 

 

Although encryption won't stop an ARP assault from happening, it can lessen the potential harm. MiTM attacks were frequently used to capture login credentials that were previously frequently sent in plain text. 

 

The increasing usage of SSL/TLS encryption on the internet has made this kind of assault more challenging. Even though the traffic is encrypted, the threat actor can still intercept it but cannot use it for anything.

 

Also Read | What is Malware? What are the signs of Malware Infection?

 

 

To Summarise:

 

With all the threats in the cyber world, there is no justification for being lax and taking a casual approach to cyber security. A significant security vulnerability, ARP spoofing can do unimaginable harm. Adopt the finest preventative measures and take proactive action to address this problem when it is still in its infancy.