You probably already know how to use SSH to securely log in toremote hosts over the Web. In this article, take things a little further byusing SSH to encrypt connections to other ports as well. Scenarios coveredinclude securing your mail server connection so that your mail password isalways protected and creating secure pathways through firewalls for trustedhosts.
Most relatively-experienced Internet users are already familiar with the benefits of SSH, secure shell technology that makes it possible to securely connect to other hosts over TCP/IP. Unlike regular telnet, which is unencrypted and offers hackers numerous opportunities to break into your connection and siphon off sensitive information, SSH is a secure communication protocol, one which is immune to IP-based attacks, and which uses hard-to-crack cryptographic techniques to protect the data it carries.
Now, most of the time, SSH is used as a replacement for regular telnet, allowing users to securely log in to other hosts on a network. However, in addition to this, SSH also comes with one very interesting - yet not very well-known - feature: the ability to create secure "tunnels" between two hosts for encrypted data communication between other ports as well. This means that, for example, you could use SSH to create a secure tunnel between your local host and your mail server so that your mail password is never transmitted in cleartext across the network (as is usually the case) every time you check your mail. Or you could use SSH to build an encrypted bridge between two or more firewall-protected hosts, so that network sniffers never get to intercept the data flowing back and forth between the two.
By allowing such encrypted connections between two (or more) hosts, SSH provides harassed network administrators with a powerful weapon in their daily balancing act of making their network more secure while simultaneously giving users as much flexibility as possible. SSH tunneling and port forwarding allow any user on a TCP-based network to communicate and transact with other hosts on the network in a reliable and secure fashion, with minimal risk of data interception or corruption.