Re: Do I need a Firewall for Ubuntu?
In IPV4 the mac address is local network only. The MAC address isn't mapped to anything in a normal IPV4 packet.
In IPV6 the original spec used the mac address because the IPV6 address space is plenty big enough to use that as a key. Privacy advocates poo-poo'd that (rightfully so IMO) so even there it's not a reliable key.
IMO the remote access thing is no big deal. You open a port on your external hardware, then send that to a specific IP and a specific port inside.
The more layers you can get the better within reason, and it's best for small office/home office (SOHO) routers to have completely separate hardware so you're positive no software flaws let the bad guys get around some security flaw. I have the cable modem plus 2 completely separate routers, the "inside" one having the radios turned off so it's much more secure.
For me, my inside network has no penetration from the outside. I can connect out on a few ports, but nothing outside can initiate a connection in.
The key to remember here is to enable what MUST be there, and deny everything else. If you turn on a service, make sure you understand what that service is and know what its weaknesses are.
Help stamp out MBR partition tables. Use GPT instead!