Default Config Files and SSH Port
/etc/ssh/sshd_config – OpenSSH server configuration file.
/etc/ssh/ssh_config – OpenSSH client configuration file.
~/.ssh/ – Users ssh configuration directory.
~/.ssh/authorized_keys or ~/.ssh/authorized_keys – Lists the public keys (RSA or DSA) that can be used to log into the user’s account
/etc/nologin – If this file exists, sshd refuses to let anyone except root log in.
/etc/hosts.allow and /etc/hosts.deny : Access controls lists that should be enforced by tcp-wrappers are defined here.
SSH default port : TCP 22