This is more related to network security than to RE. Michal Zalewski (the creator of the OUTSTANDING fenris) has written an interesting (it seems, I still do not have it) book:

Silence on the Wire
A Field Guide to Passive Reconnaissance and Indirect Attacks
by Michal Zalewski

Link is here: http://www.nostarch.com/frameset.php?startat=silence

A review can be found here: http://aplawrence.com/Books/silenceonthewire.html

Byeeeeeeeeez