Of all of the types of hacks I encountered when preparing this book, it became obvious early on that ssh would require its own chapter. The ssh tool provides a very flexible and cryptographically secure method for connecting data streams together between machines over a network. Since the command line on a Linux system essentially consists of reading data from (and writing data to) files and pipelines, ssh makes it possible to sling data around a network more or less as if everything were taking place on a single machine. It does this in a fast, safe, and intuitive way, and makes for some very interesting (and powerful) hacks.
There are a couple of versions of ssh available for Linux. We'll assume that you're using OpenSSH v3.4p1 or later in the examples for this section. OpenSSH ships with all major Linux distributions, and is available at http://www.openssh.com/.