[sagher]

Whenever you got new vps just search the topic "how to protect your vps" the most common thing is safe your SSH port by changing it from 22. and the second is make user on your linux os and use sudo command. not access it directly with root access. and the 3rd is to configure iptable is your desire. one easiest software is "ufw" you can install it with the command of "apt-get install ufw" and open only specific ports you need to be...
if you like to make a private vpn network then make it strong password protected. and for ddos protection, use cloudflare services.