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Introduction

ARP (Address Resolution Protocol) spoofing, also known as ARP poisoning, is a cyberattack where an attacker sends falsified ARP messages over a local network. This malicious activity associates the attacker’s MAC address with the IP address of a legitimate device, redirecting traffic intended for the victim to the attacker instead.

This article demonstrates how ARP spoofing can be implemented in NetSim, a network simulation tool, by modifying ARP protocol behavior and analyzing the attack’s impact.

How ARP Spoofing Works?

1. Normal ARP Behaviour: Devices on a LAN use ARP to map IP addresses to MAC addresses.
2. Spoofing: The attacker sends forged ARP replies to the victim/gateway, associating the attacker’s MAC with the IP of the gateway or target.

Example Network Scenario: 

• Attacker Node: Smart Meter A (192.168.1.10)
• Victim Node: Smart Meter C (192.168.1.12)
• Target Server: Server Collector (128.11.1.25)

Smart Meter A poisons the Data Collector’s ARP cache, making it believe Smart Meter A’s MAC address corresponds to Smart Meter C’s IP. This allows Smart Meter A to send falsified data to the Server Collector while impersonating Smart Meter C.

Network Setup in NetSim

Software: NetSim Standard v14.3, Visual Studio 2022 

Project Download Link: 

https://github.com/NetSim-TETCOS/ARP-Spoofing-v14.3/archive/refs/heads/main.zip

Follow the instructions specified in the following link to download and set up the Project in NetSim: 

https://support.tetcos.com/en/support/solutions/articles/14000128666-downloading-and-setting-up-netsim-fileexchange-projects

The simulation involves:

• Home Area Network (HAN): Smart Meters (A, B, C)

• Neighbor Area Network (NAN): Access Points

• Wide Area Network (WAN): Data Collector & Server

Key Devices:

Source Code Modifications

To simulate ARP spoofing, the following changes were made in NetSim’s source code:

ARP Protocol Modifications

1. GenerateArpRequest.c
   • Defined attacker (Smart Meter A) and victim (Smart Meter C) nodes.
   • Modified fn_NetSim_Generate_ARP_Request() to include a false IP address in ARP packets.
     
2. ARP.c
   • Added fn_NetSim_ARP_Table_Update_Log() to log ARP table changes for analysis
      

3. Application Project Modifications

• In Application.h, attacker and victim nodes were defined.
• In Database_FTP_Custom.c, the function fn_NetSim_Application_StartDataAPP() was altered to spoof the source IP in data packets.
  
• In Application.c, fn_NetSim_Application_GenerateNextPacket() was updated to maintain the spoofed IP in subsequent packets.

Simulation Configuration

• Enable packet trace prior to the simulation, by clicking on configure reports on top ribbon and disable the static ARP table by clicking on Options > Static ARP > Disable.
• Run the simulation for 10 seconds.

Results and Analysis

The screenshot below displays the NetSim packet trace with packets filtered to show Smart Meter A (the attacker node) as the transmitter. Both the ARP request and the data packets sent from the attacker node have a spoofed source IP address (192.169.0.2) instead of its actual IP address (192.169.0.3).

ARP Logs

The logs (ARP_log.csv) show manipulated ARP table entries:

Conclusion

This article demonstrated how ARP spoofing can be simulated in NetSim by modifying ARP behavior and analyzing the attack’s impact.