SSH to only 1 PC
How to make sure that nobody gets access when they attempt to log in via other location (other than office LAN)
*assuming you've already changed the default port that sshd listens to TCP1022
FROM="Source IP or hostname" ssh-rsa BLAHBLAHBLAH..
Or you could do both.
Setup SSH to only use public key authentication and set a really good password for your Linode account.