SSH Security Best Practices

At file /etc/ssh/sshd_config:

Disable Root Logins

Best: PermitRootLogin no
Good: PermitRootLogin without-password

wihout-password requires "PubkeyAuthentication yes"

Limit user Logins

AllowUsers somusername1 someusername2

Disable Protocol 1

Protocol 2

Use a Non-Standard Port

Port 2345

Use Public/Private Keys for Authentication

PubkeyAuthentication yes

Disable password authentication forcing use of keys:

PasswordAuthentication no

PS! Be sure to make generate private and public key with keys authentication

Source: https://wiki.centos.org/HowTos/Network/SecuringSSH