I'm trying to determine the feasibility of using a serial port/cable to act as a simple and cheap data diode. I'll be connecting 2 Windows PCs (1 of which is on a secured network) using a 1-way null modem serial cable. I have physically removed pin 2 (receive data) on a DB9 connector that connects to the serial port of the PC located on the secured network in hope that this will make it impossible for a hacker to gain access to the secured PC through the serial port of the unsecured PC.
I tested this setup using Hyperterminal on both PCs and it appears to be able to prevent data from being sent from the unsecured PC to the secured PC at least when using a common serial communication tool such as Hyperterminal.
However, I'm concerned whether it is possible to hack the Windows API to hijack pin 3 (TD), and use it to receive data instead. I've seen a few articles but this is not clear to me that this is possible. Has anyone attempted to do something similar?
Or should I use one-way fibre instead? I've also considered 1-way fibre but it appears to be even more complex, I've also never used fibre before, so I can't figure how it could be done using commonly available network cards and equipment - anyway it's for another topic.