We’ve said it time and again, the Arduino is a prototyping platform. In that spirit, [Doug Jackson] shows you how to conserve the expensive Arduino board and Ethernet shield by building your own Arduino Ethernet module. You may remember the ENC28j60 as a NIC for your microcontrollers. [Doug's] board makes use of that chip and adds an ATmega168 with a crystal, power regulator, breakout pins, and even a few DIP switches which can come in quite handy.

The team targeted the Intel 8255x chipset because of its open documentation and availability of compatible cards like the Intel PRO/100B. They found that sending data was very easy: Write a UDP packet to a specific memory address, check to make sure the card is idle, and then tell it to send. The receive side was slightly more difficult, because you have to intercept all inbound traffic and filter out the replies you want from the legitimate packets. Even though they were writing low level chipset specific code, they said it was much easier to implement than writing an NDIS driver. While a certainly a clever way to implement a covert channel, it will only bypass an IDS or firewall on the same host and not one on the network.

[photo: Big Fat Rat]