ARP Spoofing (also known as ARP Cache Poisoning) is a type of cyber attack based on sending malicious ARP (Address Resolution Protocol) packets by attackers to the default gateway via the local network (LAN), using it in such a way as to associate its own MAC address with the IP address of the gateway device.
Typically, the goal of associating an attacker’s MAC address with another host’s IP address, such as the default gateway, is to call any traffic designed to send that IP address through an attacker. ARP spoofing permits an assailant to snap up data frames in the network and modify or stop all traffic. Usually, it is used for opening other network-based attacks, such as session hijacking attacks, MITM attacks, or denial of service.
It is important to note that only networks using Address Resolution Protocol can use this attack. As a result, the attacker will have direct access to the network segment. In addition, ARP is indeed a commonly used protocol whose algorithms convert Internet layer addresses to the link layer.
No matter whether requested by the network host or not, any Address Resolution Protocol replies received will be automatically cached. When it receives a new ARP reply, all records, including those that have not expired, will be overwritten. Address Resolution Protocol can not authenticate the peer from which the packet was sent because it has no method. This is the vulnerability that is possible to ARP Cache Poisoning.
ARP Spoofing (ARP Cache Poisoning) Attack
Because the ARP protocol does not have authentication, this allows spoofing ARP by sending spoofed ARP messages within the local network. Such attacks will be run from an infected host in the local network or from the attacker’s device, which should be connected to the same network as the target.
The task of such an attack is to associate the attacker’s MAC address with the target host’s IP address so that all traffic going to the target host will pass through the attacker’s host.
An attacker can inspect traffic (spying) and continue sending to the target host without revealing himself, modify content before forwarding (man-in-the-middle attack), or launch an attack that partially or wholly interrupts packets transferring in the network.
Detect and Prevent ARP Spoofing
Software that specializes at detecting ARP Cache Poisoning typically uses a specific form of certification or cross-checking of ARP responses. Thus uncertified ARP responses are blocked. Typically, these methods are integrated with a DHCP server to certify dynamic and static IP addresses.
An Address Resolution Protocol spoof attack indicator may be the presence of multiple IP addresses tied to the same MAC address, although sometimes the use of such a scheme is legitimate. The device analyzes Address Resolution Protocol replies and sends an email notification if the ARP record is changed in a more passive approach.
How Do I Protect Myself From an ARP Cache Poisoning Attack?
- Don’t Rely on Trust Relationships: Trust relationships use IP addresses for authentication, a method that is particularly vulnerable to ARP spoofing. Instead of relying on IP addresses alone, enhance your security by implementing robust authentication mechanisms. Create unique logins and passwords for users, and define clear security policies. These measures ensure that each user is properly authenticated and authorized, reducing the risk of unauthorized access.
- Implement Packet Filtering: Use packet filtering to control the data entering and leaving your network. This is typically handled by a firewall, which acts as a barrier between your trusted internal network and the untrusted public internet. By configuring your firewall to inspect, allow, or block packets based on protocols, source and destination IP addresses, and port numbers, you significantly enhance your network’s security. Effective packet filtering can prevent malicious data packets from being sent or received, thwarting potential ARP spoofing attempts.
- Employ Static ARP: For environments with critical or static systems, consider using static Address Resolution Protocol, where you manually enter ARP entries into the device’s ARP cache. This approach binds IP addresses to specific MAC addresses, making it much harder for attackers to insert fraudulent ARP messages into the network. Adding a permanent record in the ARP cache provides an additional layer of protection against spoofing attacks and ensures that your devices communicate only with authenticated counterparts.
How to Employ Static ARP
Static Address Resolution Protocol (ARP) entries are a network security measure used to prevent ARP spoofing by manually binding an IP address to a Media Access Control (MAC) address. This ensures that the network interface card (NIC) only allows communications from a specific MAC address on a given IP address. Here’s a step-by-step guide on how to set up static ARP entries on a network:
1. Determine the IP and MAC Addresses
To find the IP and MAC addresses of the devices on your local network, you can use the ARP command. This command helps view and manage the ARP table, which links IP addresses to their corresponding MAC addresses on your network.
- Open Command Prompt: Press Win + R, type cmd, and hit Enter.
- View ARP Table: Type arp -a in the command prompt and press Enter. This displays a list of all active IP addresses and their associated MAC addresses.
Example of ARP Output:
Internet Address Physical Address Type
192.168.1.1 00-14-22-01-23-45 dynamic
192.168.1.2 00-14-22-01-23-46 dynamic
2. Access Your Router or Switch
Log into your network router or switch that manages ARP tables. You will need administrative access to modify ARP settings.
3. Navigate to the ARP Settings
Find the section in the router or switch’s admin panel that deals with ARP settings. This section might be labeled as “ARP Table”, “Static ARP”, “Security Settings”, or something similar.
4. Add Static ARP Entries
Within the ARP settings, select the option to add a new ARP entry. Enter the IP address and the corresponding MAC address of the device. Ensure that you enter these details correctly to avoid network issues.
5. Save and Apply Changes
After entering the details, save the changes and apply them. It is important to ensure that the ARP table is correctly updated across the network.
6. Verify the Static ARP Entry
Verify that the static ARP entry is working as intended. You can do this by checking the ARP table in the router or switch to see if the entry appears as static. Additionally, you might want to test network connectivity from the device to confirm that it can communicate securely and effectively.
7. Continuous Monitoring and Management
Static ARP entries require ongoing management to ensure they remain effective and accurate. Regularly review and update the ARP table as needed, especially when new devices are added to the network or when network configurations change.
Using static ARP entries effectively reduces the risk of ARP spoofing attacks by ensuring that IP addresses on your network are paired reliably with their legitimate MAC addresses. However, managing static ARP can become complex in larger networks, so it’s often complemented with other security measures like dynamic ARP inspection on switches.
