If I own a private IP address, 192.168.2.1 for the sake of it, and I am physically connected to my router, which it's internal interface is 192.168.2.254 and it's external interface is some public IP address which it got from my ISP's DHCP server.
Obviously my IP is being translated over NAT so I can surf the internet.
So how can someone hack into my computer?
Looking at it from the OSI model perspective:
- Layer 1 - Irrelevant
- Layer 2 - ARP attacks, only people who live in my home and share the same network, irrelevant for the sake of discussion
- Layer 3/4 - Well, my IP is a private one, so people can't really probe me for open ports and vulnerabilities, right? They can probably probe my router, but it's just a "ISP smart box", which isn't really a router (although it operates also as a Wifi AP, so people will need to crack it in order to get something done)
- Layer 5 and up - These are the only layers which I will be vulnerable to an attack, am I right? Ranging from XSS, to some other things?