SSH

SSH is a network protocol generally used to provide secure shell access remotely (although it can technically be used to transmit anything). The protocol has various implementations. We use OpenSSH. (man page)

SSH Client

You can type ~. into your SSH client to disconnect it. This is useful for when a connection freezes.

OpenSSH Configuration

For the love of god, turn off password authentication and root login. You can do so with the following directives in /etc/ssh/sshd_config:

PermitRootLogin no
PasswordAuthentication no

You can also further lock down access with:

AllowGroups users

This makes sure only members of the group, users can authenticate over SSH reduces the attack surface for accounts that should never be accessed by a user. You can obviously substitute users for another group of your choosing.