I used Wireshark (http://www.wireshark.org/). I was actually diagnosing a different issue, until I noticed that my Win8 machine was especially chatty. When I looked more into it, I was horrified as to how much data was being uploaded to Microsoft. I used many different techniques, including Man in the Middle in order to see what info was actually being sent. It was especially creepy to see that the Win8 box took evasive actions as I tried to spy on its communications. I wonder exactly what Microsoft has to hide regarding this communication and has to encrypt it and be evasive.

I am not aware of any easy way of monitoring BIOS level communications. If you are afraid that the BIOS has been compromised by a virus then I would suggest that you update the BIOS with an update from the vendor's web site. Even if it the same version that's installed.

If you are worried that the machine's vendor has somehow added spying routines into the BIOS, then for safety's sake don't use the machine for work, or for any secure info. Use it only play.