SSH is considered a secure alternative to older protocols, such as Telnet, rsh, and rlogin, because it encrypts the connection between the client and server. This encryption protects the traffic from any ne'er-do-wells who may be eavesdropping on the network. However, your system can still fall victim to the denial of service attacks or a malicious user who takes advantage of an idle session that was carelessly left unattended. This recipe takes the first steps in hardening SSH by updating the server's configuration to increase security surrounding remote logins.
This recipe requires a CentOS system running the OpenSSH server. Administrative privileges are also required, either by logging in with the root account or through the use of sudo.