content: OSI and "encryption" Let me just rely on the OSI model for now. One thing I've seen a lot is that "encryption" is a function that operates at the presentation layer (6). Yeah, sure, fine. I can see that. But as you ... collect? taxonomize? the protocols of different layers, you might run across... half-remembered gems -- like NetBIOS, or PPP. Then, thinking about layer 2, I can imagine tapping a signal or playing with WireShark, but what if the signal is weird? If there's FIDDI and X.25, then there must be weirder implementations. I would imagine that it is quite possible that there are "one-off" implementations among engineers who are only using 2 machines to do something very particular. Granted, that's "security through obscurity" but I can imagine several overlapping layers of encryption.  Does anybody know anything about encryption at multiple layers, or strange WI-FI signals that are not 802.11, or presentation protocols that are not in ASCII (like that weird 7-bit standard used by that huge 5-meg hard drive.) How weird can it get? Are there any urban legends akin to the Russian Woodpecker? "There was a signal, man, but no header, no nothin'! Just like static, but wouldn't quit! And Mossad was pumping 50,000 watts into it, but no one could even receive it, man..."