I'm not a security expert by any means, but I like these three guides in the DO tutorials for a typical box. https://www.digitalocean.com/community/tutorials/a

I'm not a security expert by any means, but I like these three guides in the DO tutorials for a typical box. https://www.digitalocean.com/community/tutorials/an-introduction-to-securing-your-linux-vps https://www.digitalocean.com/community/tutorials/an-introduc... https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys--2 https://www.digitalocean.com/community/tutorials/how-to-set-... https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-on-ubuntu-14-04 https://www.digitalocean.com/community/tutorials/how-to-secu... There are a dozen or so tools mentioned in the above.