a binary driver blob can do a better job at backdooring. or even dare to say, the hardware, network card, may have already had one built into it at the factory. i vote for a mostly fudd value of this info.
which can be backdoored, and would then be impossible to detect from the operating system.
http://esec-lab.sogeti.com/dotclear/index.php?post/2010/11/2...