Originally Posted by PMP
Yes It is possible
It certainly is. If you're running sshd (ssh daemon) anyone with a username and password can login unless you've locked them out. if you are on a router or switch, or hub, you need to port forward port 22 on that device. that is ssh's port usually. goto this address: http://www.whatismyip.com/
and have the user input that address. i'd use
ssh -l username 76.25.x.x (whatever that address is)
If you're not running sshd type sshd in the terminal. If you don't have it installed, go into your package manager and get it. although every system i've had has shipped with it.