You have several options how to block your PS3 from accessing internet while still working on your home network. You can either set manually DNS servers to some invalid address - like 18.104.22.168 or try to also remove default gateway (it might not work afterwards though even for the streaming itself) or assign your PS3 with fixed IP and then block that IP from accessing internet in your router.
Originally Posted by tardor
you can't kill the ps3 internet connection. but why would you ?
I believe you've meant "you can" and to your question - because you don't want to Sony spy on you while using JB - read the main page news as well as several threads in the Hack section regards stealth backup managers etc.