Blog | G5 Cyber Security

Stop ARP Poisoning Attacks

G5 Cyber Security

TL;DR

ARP poisoning attacks let someone intercept your network traffic by faking network addresses. This guide shows you how to spot them and protect yourself, from simple checks to more advanced solutions.

What is ARP Poisoning?

Address Resolution Protocol (ARP) translates IP addresses (like 192.168.1.10) into MAC addresses (unique hardware identifiers). An attacker sends fake ARP messages, linking the wrong MAC address to a legitimate IP address. This redirects traffic through their machine, allowing them to eavesdrop or modify data.

How to Detect an Attack

  1. Slow Network Performance: A sudden drop in speed can be a sign.
  2. ARP Cache Inspection: Check your ARP table for inconsistencies. On Windows: 
    arp -a

    On Linux/macOS:

    arp -an

    Look for multiple MAC addresses associated with the same IP address – this is a red flag.

  3. Network Sniffing: Tools like Wireshark can capture network traffic and reveal suspicious ARP replies. Filter by ‘arp’ to focus on ARP packets.

Protecting Your Network

  1. Static ARP Entries (Advanced): Manually define the IP-to-MAC address mappings for critical devices. This prevents attackers from spoofing these entries. 
    arp -s 192.168.1.1 00:1A:2B:3C:4D:5E

    (Replace with your actual IP and MAC addresses). This needs to be done on each machine, and is best for a small, controlled network.

  2. Port Security (Switches): Configure switches to only allow traffic from known MAC addresses on specific ports. This limits the attacker’s ability to inject fake ARP packets.
    • Most managed switches have this feature in their web interface.
    • Set port security to ‘static’ and bind it to a single MAC address.
  3. DHCP Snooping (Switches): Prevents rogue DHCP servers from distributing incorrect IP addresses, which can be used in conjunction with ARP poisoning.
    • Enable DHCP snooping on your switch.
    • Configure trusted ports where legitimate DHCP traffic is expected.
  4. Dynamic ARP Inspection (DAI) (Switches): Validates ARP packets and filters out malicious ones.
    • Enable DAI on your switch.
    • Requires DHCP snooping to be enabled first.
  5. Use Strong Encryption: HTTPS (SSL/TLS) encrypts data in transit, making it unreadable even if intercepted.
    • Ensure websites you visit use HTTPS. Look for the padlock icon in your browser.
  6. Keep Software Updated: Regularly update your operating system and network drivers to patch security vulnerabilities.
  7. Firewall: A firewall can block suspicious traffic patterns associated with ARP poisoning attacks.
    • Configure rules to drop packets from unknown sources.

Tools for Prevention

  1. Anti-ARP Poisoning Software: Some cybersecurity software packages include features specifically designed to detect and prevent ARP poisoning attacks.
  2. Network Monitoring Tools: Regularly monitor your network for unusual activity using tools like Wireshark or intrusion detection systems (IDS).
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