Using SSH to log into UNIX servers at FIU-CIS

December 29, 2003

Introduction

Some people are still using telnet and rlogin to log into UNIX servers. These protocols are outdated and insecure, so they are slowly being phased out here at FIU-CIS. For this reason, we have created this page to educate our user community about SSH and why it's important that everyone use it.

The telnet and rlogin protocols are completely unencrypted. When you telnet or rlogin to another machine, your login and password are transmitted over the network in the clear. Anyone who is listening on your network segment or at any router on the path between the machines can steal your password and compromise your account.

SSH changes all this. When you SSH to a host, the entire session is encrypted. There are several encryption types, one of the common ones being 3des. This encryption protects your session from prying eyes and keeps your account and our servers much safer.

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Clients

There are many SSH clients available for many different architectures. Here is a quick list of the best clients for each architecture and where to get them.

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Unix

Many UNIX distributions come with an SSH client and server already installed. One of the best SSH packages for UNIX is OpenSSH . It is entirely free and open-source. It is also well-maintained, so security problems are generally found and resolved quickly. To use OpenSSH to log into a server, simply type ssh username@hostname at a shell prompt, then enter your password.

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Windows

One of the smallest and easiest to install SSH clients for Windows is PuTTY . It is distributed as a single executable file which contains everything needed to run it; no external DLL's or other baggage. To use PuTTY, just execute it and enter a hostname. If this is the first time you ssh to this host, you will be asked to add the host's key to your list of known hosts. Go ahead and do so, enter your password at the prompt, and you should then be logged in.

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MacOS X

MacOS X is a UNIX system underneath, and comes with OpenSSH. Simply open up a terminal window and type ssh username@hostname at the shell prompt and you will be able to log in.

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Phasing out of telnet and rlogin

After major upgrades, you may find yourself no longer able to telnet and rlogin to hosts. For this reason, it is very important to migrate to SSH as rapidly as you can. If you are associated with FIU-CIS and have any questions, feel free to contact us at request@cis.fiu.edu.