[CentOS] two questions about ssh tunneling

>if I:
>
>ssh -fND localhost:6000 somebody at 192.168.56.5 -p PORTNUMBER
>
>from computer "A" to computer "B" [B = 192.168.56.5] then I can set the SOCKS proxy for e.g.: Firefox to use "localhost:6000" on computer "A". Ok. I can surf the web through "B".
>
>But:
>- Can anyone sniff the traffic of "A"? [e.g.: computers on same subnet as "A"] Like DNS requests? - I think no, but I'm not sure :O

Sure, that possible if your name resolution traverses a network path interceptable
by the guy sniffing.

>- Can anyone sniff the traffic of computer "B"? e.g.: B computer is at a server farm [others in the farm can see the traffic?] - I think yes, but I'm not sure :O

Same thing, if the outbound web traffic leaves that host via a route another op has
access to, like a switch with a mirror port, he can easily see what's moving back and
forth.