Locking down remote access and hardening SSH

In this recipe, we will learn how to provide additional security measures in order to harden the secure shell environment. The Secure Shell (SSH) is the basic toolkit that provides remote access to your server. The actual distance to the remote machine is negligible, but the shell environment enables you to perform maintenance, upgrades, the installation of packages and file transfers; you can also facilitate whatever action you need to carry out as the administrator in a secure environment. It is an important tool; as the gateway to your system, it is the purpose of this recipe to show you how to perform a few rudimentary configuration changes that will serve to protect your server from unwanted guests.

Getting ready

To complete this recipe, you will require a minimal installation of the CentOS 7 operating system with root privileges, a console-based text editor of your choice, and a connection to the Internet in order to download additional packages...