A minimal improvement to your security is asking for a password when you allow normal users to execute privileges command via sudo. Usually, they just type their own password and that allows they to gaing privileged status to execute what you have set in sudo files.
You should consider change this behaviour and ask for root password. Why? it’s too easy IMHO to execute a root command because the user (or impostor) only needs to know one single password and not your root password but someone elses one.
Instead of that setting I prefer to change sudo files to this in the /etc/sudoers:
Before do that, be sure your root password is setted and accomplish a minimul security recommendations. It will not apply in current shells, but the new ones.