Security Implications of SSH

As an updated and secured version of older protocols such as Telnet and FTP, SSH is being installed and enabled on an increasing number of devices, from personal desktops to firewalls. There has been significant discussion on the whys and wherefores of the installation of SSH, the benefits of SSH over earlier protocols, and even how to set up tunneling to secure communication for other protocols via SSH. I have thus far seen little discussion on the potential security exposure offered by SSH and how to mitigate that exposure. This paper was written to provide a high-level discussion of some of the security considerations associated with SSH as well as some potential methods of addressing those considerations. SSH is a useful protocol, but to be a true benefit to an organization, it must be implemented with some care. Evaluation of where in an architecture it is installed as well as some configuration suggestions can significantly increase the security of the overall implementation.