I'm a newbe so bear with me.
When I recently set up my HD system, I decided on the Sony PS3 as my Blu-ray player (I know Sony DANGER, DANGER!). My system is more than 50 feet from my computer room, but it immediately detected my wireless network, and went on line. I let the PS3 update its firmware, but looked in all the setup menus, and finally found an entry for turning off Inet access. It seems to work, because when I put a Blu-ray movie on, and go to my computer room, neither my wireless routers Inet light nor my satalite modem light show any activity. I have also watched these lights many time when no movie is being watched, no activity shows unless I initiate it from my computer.
So yes they can make you go on line, untill you find out how to turn off Inet access for the player.
when them lights flash that doesn't always mean theres activity per say, your network devices when connected will communicate with one another, (ping one another) this keeps the connections active between them devices, my modem indicates activity even with my computers disconnected unplugged etc, as longs my router and switch are connected, or sometimes with the modem alone as it ping the ISP to keep the connection alive, this does not mean it's sending or receiving data off and on the INTERNET,
perhaps someone here can explain it a little better. but yes them lights do indicate file or data transfer activity as well, but it don't indicate that alone is my point I'm trying to make with the lack of proper fancy wording,