FireSSH is an open source cross platform browser based SSH terminal client extension for Firefox, developed by Mime Čuvalo using JavaScript for handling accessible and reliable remote SSH sessions right from the browser window
By default, SSH already uses a secure data communication between remote machines, but if you want to add some extra security layer to your SSH connections, you can add a Google Authenticator (two-factor authentication)
pam_tally2 module is used to lock user accounts after certain number of failed ssh login attempts made to the system. This module keeps the count of attempted accesses and too many failed attempts. pam_tally2