Introduction

With the massive increase in the use of computers and networks for communication, there has also been an increase in the presence of hackers and unethical attacks on such networks to steal information and wreak digital havoc. ARP spoofing, also called ARP poisoning, is one such method that is used by hackers to intercept communications between two devices on the same Local Area Network (LAN).

  1. What is Address Resolution Protocol (ARP)?
  2. What is ARP Spoofing? 
  3. Prevention of ARP Attacks

1. What is Address Resolution Protocol (ARP)?

To understand what is ARP spoofing, one must first understand Address Resolution Protocol and its functioning. For communications over a Local Area Network (LAN), there is a need for the mapping of dynamic Internet Protocol (IP) Addresses to the physical permanent address of the device or the machine involved in the communication process and this is where ARP comes into play. In simple words, ARP is a network protocol that translates 32-bit IP addresses to 48-bit MAC (Media Access Control) addresses to enable efficient communication on a Local Area Network.

Therefore, the ARP sends out broadcast requests to all machines on the LAN when there is an attempt to communicate with a particular IP Address, and the machine bearing that IP Address then responds to this request with the MAC address (also called an ARP reply) which enables free and unrestricted data transfer and communication. The problem of ARP attacks, however, arises when the ARP reply is intercepted by hackers to hijack information. 

2. What is ARP Spoofing? 

An ARP spoofing man in the middle attack (MitM), sometimes referred to as an ARP poisoning attack, is one where attackers exploit the Address Resolution Protocol (ARP) in order to intercept all communications between two devices on the same network. What primarily makes ARP spoofing possible that the protocol was not designed to be a security feature but a mere communication tool and it, therefore, lacks a verification procedure to ascertain the legitimacy of ARP responses received over the network.

An attacker can therefore send an ARP reply to any request on the network containing incorrect information to manipulate the ARP. This is what is ARP poisoning. This is what is exploited by attackers as the device that is seeking to establish a channel of communication accepts any ARP response and registers the MAC address of the attacker’s machine for all future communications with that IP address. From that point onward, the individual who has initiated the ARP spoofing attack gains full access to all communications between the two target devices. 

The following are the steps that an attacker usually follows to orchestrate an ARP attack. 

  • The attacker gains access to the network and identifies the IP address of at least two devices on the same network. 
  • The attacker then uses an ARP spoofing tool in order to send out forged ARP replies on the network which leads to ARP cache poisoning.
  • The fake ARP response convinces both devices that the MAC address of the attacker’s system is the right one and thereby both devices end up connecting to that system instead of each other. 
  • Once connected, the ARP cache entries are updated for all future communications and the attacker thereby gains access to any and all communications between the two devices.

If an attacker succeeds in an ARP spoofing attack, he has a wide range of options with which he can steal or intercept sensitive communications or cause disruptions in services. Unless data packets are encrypted, the attacker will be easily able to hijack and steal information from all communications between the two devices.

In some cases, the hacker might be able to steal the session ID of a logged-in user and impersonate them through session hijacking methods. The hacker can also easily push malicious files or websites to the devices to cause disruptions or to facilitate data theft. Since there are many such risks that can arise from such attacks, it is very important for organizations and individuals to learn how ARP spoofing works as well as how to defend against ARP spoofing.

3. Prevention of ARP Attacks

When an attacker has successfully executed an ARP spoofing attack, ARP cache poisoning is the result that allows for all future communications to pass through the same fake MAC address that has been fed to the ARP protocol and stored in the ARP cache. Thankfully, however, there are several ways by which one can detect an ARP attack. The first option is to utilize the Command Prompt tool as an administrator on a Windows PC and bring up the ARP cache on the Command Prompt window by entering ‘arp -1’.

If two devices with different IP addresses are seemingly sharing the same MAC address, it is highly likely that you are undergoing an ARP poisoning attack. There are also other ARP spoofing Windows tools and programs available that are designed to detect any incidence of ARP attacks and notify the user of the same. To enable efficient ARP spoofing defense, an organization must therefore necessarily know how ARP spoofing python scripts work and how to detect ARP spoofing attacks as early as possible. The following are some useful ways in which ARP spoofing prevention can be achieved. 

  1. Using a Virtual Private Network (VPN): Virtual Private Network (VPN) services are available widely for reasonable and affordable prices and these networks allow devices to connect and communicate over the internet through a secure and encrypted tunnel that renders any attempt to spoof the ARP worthless. This is because no data can be stolen or accessed by the attacker.
  2. Packet filtering: There are certain packet filters that are able to analyze all the data packets that are sent through a particular network and detect and block any packets that are malicious or have been sent from suspicious IP addresses. The filters are also capable of detecting packets that are supposed to be sent internally on a Local Area Network (LAN) but are originating externally, thereby reducing the chances of a successful ARP attack. 
  3. Use static ARP entries: If feasible, individual ARP entries may be added to each device on a local network and therefore the device MAC and IP addresses are mapped manually. When these addresses are made static, the device ignores any and all ARP replies or responses that are necessary to execute a spoofing attack. 
  4. Encryption: Data can be encrypted by using certain encryption protocols that make it difficult for the attacker to steal and access information that is being sent through the network. SSH and HTTPS are some examples of encryption protocols.

Conclusion 

Since no defense mechanism against ARP spoofing can be absolute, there needs to be a good system in place to detect such attacks and if any such attack is detected, there must be quick action to shut it down in order to greatly minimize the damage done. 

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