NJam is a simple network jamming tool written in C that disrupts local network traffic by performing ARP spoofing. This technique allows you to poison the ARP cache of devices on a network, redirecting their traffic to the wrong MAC address (yours). The inspiration for this project came from the arpspoof tool, which works well but is limited to targeting a single device at a time. NJam was created to scale this attack and disrupt entire networks more effectively.

NJam performs ARP spoofing, which relies on the fundamental behavior of the ARP protocol.

ARP (Address Resolution Protocol) is used to map IP addresses to MAC addresses on a local network.

Here's an example structure of an ARP packet:

1. Hardware Type
   Defines the type of hardware at the link layer.

   • Common value: 0x0001 for Ethernet.

2. Protocol Type
   Defines the upper-layer protocol.

   • Common value: 0x0800 for IPv4.

3. Hardware Length
   Length in bytes of the hardware address.

   • Common value: 6 (for MAC address).

4. Protocol Length
   Length in bytes of the protocol address.

   • Common value: 4 (for IPv4 address).

5. Operation Code
   Indicates the type of ARP message:

   • 1 – ARP Request
   • 2 – ARP Reply
   • Rare values: Reverse ARP, InARP, etc.

6. Addresses

   • Sender Hardware Address (SHA): MAC address of the sender (spoofed in our case).
   • Sender Protocol Address (SPA): IP address of the sender (spoofed to appear as a legitimate device).
   • Target Hardware Address (THA): MAC address of the device we are targeting.
   • Target Protocol Address (TPA): IP address of the target device.

1. Discovery Phase:
   Get MAC addresses of the router and target device using ARP requests.

2. Spoofing Phase:
   Send crafted ARP reply packets:

   • One with the sender IP of the router and our MAC address to the target.
   • One with the sender IP of the target and our MAC address to the router.

In both cases, we trick each side into associating our MAC with the IP of the other side.

3. Effect:
   Packets intended for the router or target are instead sent to our device, allowing for disruption or potential man-in-the-middle attacks.

• src/ – C source files
• include/ – C header files
• packaging/ – Packaging used for .deb
• images/ – Diagrams and packet structure
• build.sh – Executable script to build project