How to Stop a Confirmed ARP Spoofing Attack Using Kali Linux: Step-by-Step Guide

When you confirm an ARP spoofing attack on your network, it is crucial to act quickly and take the necessary steps to secure your devices and network. This guide will walk you through how to stop the attack using Kali Linux, a powerful penetration testing and security auditing platform. We will also cover the tools you’ll need and the best practices for securing your network.

Step 1: Confirm the Attack

Before taking any action, you must ensure that the ARP spoofing attack is indeed happening.

Tool: Wireshark

• Wireshark is a packet sniffing tool that captures and analyzes network traffic in real-time.
• Steps:
  1. Launch Wireshark on Kali Linux.
  2. Choose the network interface you suspect is under attack (e.g., eth0 for Ethernet or wlan0 for Wi-Fi).
  3. Apply a filter to monitor ARP packets: arp.
  4. Look for unusual ARP replies, especially duplicate IPs with different MAC addresses.

If you notice duplicated IPs with different MAC addresses, it’s a sign of an ARP spoofing attack.

Step 2: Identify the Attacker

You need to pinpoint which device on the network is conducting the ARP spoofing attack.

Tool: Arp-scan

• Arp-scan is a network scanning tool that can help you discover all devices on your network.
• Steps:
  1. Run sudo apt-get install arp-scan to install the tool if it isn’t already installed.
  2. Use the command sudo arp-scan -l to scan the local network.
  3. Compare the MAC addresses of all devices on your network. Look for mismatched IP-MAC pairs or unknown devices.

Once you identify the attacker’s IP and MAC address, you can proceed to block or remove them.

Step 3: Block the Attacker

Now that you have identified the attacker, you can block their access to the network.

Tool: iptables

• iptables is a built-in firewall tool in Linux that you can use to block specific IP addresses or MAC addresses.
• Steps:
  1. Block the attacker’s IP address with the following command: sudo iptables -A INPUT -s <attacker-IP> -j DROP
  2. To block a specific MAC address, use: sudo iptables -A INPUT -m mac --mac-source <attacker-MAC> -j DROP
  3. Verify that the rule has been added using: sudo iptables -L

This will stop the attacker’s traffic from entering your network.

Step 4: Clear ARP Cache

An ARP spoofing attack alters the ARP cache of your system, associating incorrect MAC addresses with legitimate IP addresses. You need to flush your system’s ARP cache to remove the corrupted entries.

Tool: iproute2 (ip command)

• Steps:
  1. Run the following command to clear your ARP cache: sudo ip -s -s neigh flush all
  2. This command will remove all current ARP entries from your cache, forcing your system to rebuild it with fresh and correct information.

Step 5: Implement ARP Spoofing Prevention

Once you have blocked the attacker and cleaned up your network, it is time to prevent future ARP spoofing attacks.

Tool: arptables

• arptables is a firewall utility for controlling ARP packet filtering.
• Steps:
  1. Install arptables with sudo apt-get install arptables.
  2. Add static ARP rules for critical devices. For example: sudo arptables -A INPUT --source-mac <router-MAC> -j ACCEPT sudo arptables -A INPUT --source-ip <router-IP> -j ACCEPT
  3. Set up rules to drop other suspicious ARP packets: sudo arptables -A INPUT -j DROP

This ensures that only legitimate ARP requests and replies from known devices (like your router) are accepted.

Step 6: Monitor the Network Continuously

After securing the network, you should set up continuous monitoring to detect and prevent future attacks.

Tools:

• Wireshark (for packet analysis)
• arpwatch (to monitor ARP activity and report changes)
  • Steps:
    1. Install arpwatch: sudo apt-get install arpwatch.
    2. Start arpwatch: sudo service arpwatch start.
    3. arpwatch will send you alerts when new devices or ARP changes are detected on the network.

These tools will provide real-time alerts and logs for any suspicious ARP activity.

Best Practices for Securing Your Network:

1. Use Static ARP Entries: For critical devices like your router, manually configure static ARP entries. This prevents ARP spoofing by ensuring that IPs always resolve to the correct MAC addresses.
   • Example for a static ARP entry: sudo arp -s <router-IP> <router-MAC>
2. Enable MAC Address Filtering on Router: Configure your router to only allow certain MAC addresses to connect.
3. Use VPN for Encrypting Traffic: A VPN can help protect your network traffic from being intercepted during a man-in-the-middle attack.
4. Regularly Update Your Devices: Ensure that your systems, routers, and network devices are up to date with security patches.

Conclusion

When dealing with ARP spoofing attacks, the key is to act quickly to block the attacker, secure your devices, and implement long-term preventive measures. Using Kali Linux and tools like Wireshark, arp-scan, iptables, and arptables, you can effectively identify the attack, stop it, and protect your network from future threats. Continuous monitoring and proactive network management will help ensure your network remains secure.

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