ARP spoofing is a type of cyber attack where a hacker sends fake Address Resolution Protocol (ARP) messages to a local network. This can be dangerous. Think of ARP as a phonebook that matches IP addresses (house addresses) with MAC addresses (house phone numbers). If someone gives you a fake phonebook, you might call the wrong house. In the digital world, this means data might go to the hacker instead of its rightful destination.
To help you safeguard against such threats, we’ll learn how to detect ARP spoofing using Scapy, a Python library. Before we dive in, let’s ensure we’re clear on some terms.
Definitions:
- ARP (Address Resolution Protocol): This protocol matches IP addresses with MAC addresses. It’s like the bridge between the internet and physical devices.
- Scapy: A powerful Python library used to analyze, manipulate, and create packets in a network.
- ARP spoofing: A technique where false ARP messages are sent over a local network to link the hacker’s MAC address with the IP address of a legitimate computer or server.
- MAC address: A unique identifier assigned to network interfaces. Think of it as the ‘phone number’ for devices in a local network.
- IP address: A unique address that identifies a device on the Internet or a local network, like the ‘house address’ in our phonebook analogy.
How does ARP Spoofing Work?
- Legitimate ARP Request: Device A asks, “Who has this IP address? Please tell me the MAC address.”
- Legitimate ARP Reply: Device B responds, “I have that IP. Here’s my MAC address.”
- Spoofed ARP Reply: Hacker device interrupts and says, “Actually, that IP is associated with my MAC address.”
Now, Device A is tricked into sending data to the hacker.
Detecting ARP Spoofing with Scapy
Step 1: Install Scapy
pip install scapy
Step 2: Writing the Python Code
import scapy.all as scapy
# Create a dictionary to store IP to MAC mappings
ip_mac_mapping = {}
def process_packet(packet):
if packet.haslayer(scapy.ARP) and packet[scapy.ARP].op == 2: # 2 means ARP reply
ip = packet[scapy.ARP].psrc
mac = packet[scapy.ARP].hwsrc
if ip not in ip_mac_mapping:
ip_mac_mapping[ip] = mac
print(f"[+] Detected new device: {ip} -> {mac}")
elif ip_mac_mapping[ip] != mac:
print(f"[!!] ARP Spoofing Alert: {ip} has multiple MACs: {ip_mac_mapping[ip]} and {mac}")
# Start sniffing the network
scapy.sniff(prn=process_packet, store=False)
What’s Happening in the Code?
- We first import necessary modules from Scapy.
- We set up a dictionary (
ip_mac_mapping) to track IP to MAC relations. - The
process_packetfunction checks each network packet:- If it’s an ARP reply, it records or compares the IP to MAC mapping.
- If the mapping changes (different MAC for the same IP), it raises an alert.
scapy.sniff()starts monitoring network traffic, processing each packet with our function.
Code Explanation
- We import what we need: ARP for address things and sniff to peek into traffic.
- We create a dictionary to remember which IP belongs to which MAC.
- In the function, for every packet:
- We check if it’s ARP.
- Get the source IP and MAC.
- If we know this IP and its MAC doesn’t match our record, it might be an attack.
- If it’s a new IP, we remember it.
- Finally, we start peeking into traffic, focusing on ARP packets.
Protecting Against ARP Spoof Attacks Awareness is the first step. Now that you know how to detect ARP spoofing, consider these steps:
- Static ARP: Just like saving a number on your phone so you know who’s calling, you can manually save IP-MAC pairs.
- Use VPN: A Virtual Private Network (VPN) is like a safe tunnel. Even if someone intercepts, they can’t see inside.
- ARP Spoof Detection Tools: There are tools like
Arpwatchwhich continuously monitor ARP changes.
Conclusion
ARP spoofing can compromise network security, but tools like Scapy make detection easier. By understanding the basics and maintaining vigilance, you can prevent unwanted intruders from tampering with your network communications.
