Securing Tinker Board SSH

1. Require the sudoer to prompt for a password by updating the /etc/sudoers file with the following:
   Look for the following:

   %sudo ALL=(ALL) NOPASSWD: ALL

   And update to become the following:

   %sudo ALL=(ALL) ALL

2. Update the /etc/ssh/sshd_config file to have the following added:

   PermitRootLogin no

3. Install fail2ban using the following command:

   sudo apt-get install fail2ban

4. Create the file /etc/fail2ban/jail.d/jail.ssh file to have the following:

   [ssh]
    enabled = true
    port = ssh
    filter = sshd
    logpath = /var/log/auth.log
    maxretry = 6
    bantime = -1
    banaction = iptables-allports

5. Restart the service using the following command:

   sudo systemctl restart fail2ban

See Unbanning an IP