You already have the password protect option to stop unauthorised change of the BIOS data that can be set in the BIOS and there is the No-Execute Memory Protect that can stop certain BIOS virus actions.
I tested that even with a password set I could easily overwrite the bios in windows with @bios, it does not prompt for a password, just happily overwrites the bios. If there is a way to prevent this I would love to hear it.
These new viruses dump your bios edit it then write the edited version back, because of this bios updating outside the bios (from windows) needs to be disabled, I have the equipment to lift the bios write pin and put in a switch but a software solution like a simple bios option that would not void my warranty would be a nice piece of mind on my brand new $200 board.
The problem is also outlined here
http://www.jupiterbroadcasting.com/12136/ultimate-home-router-techsnap-23/ by some IT experts
look at the section "BIOS rootkit found in the wild" or watch the show