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+\define{versionidintro} \versionid $Id$
+
 \C{intro} Introduction to PuTTY
 
-\# PuTTY is an SSH and Telnet client
+PuTTY is a free SSH, Telnet and Rlogin client for 32-bit Windows
+systems.
+
+\H{you-what} What are SSH, Telnet and Rlogin?
+
+If you already know what SSH, Telnet and Rlogin are, you can safely
+skip on to the next section.
+
+SSH, Telnet and Rlogin are three ways of doing the same thing:
+logging in to a multi-user computer from another computer, over a
+network.
+
+Multi-user operating systems, such as Unix and VMS, usually present
+a \i{command-line interface} to the user, much like the \q{\i{Command
+Prompt}} or \q{\i{MS-DOS Prompt}} in Windows. The system prints a
+prompt, and you type commands which the system will obey.
+
+Using this type of interface, there is no need for you to be sitting
+at the same machine you are typing commands to. The commands, and
+responses, can be sent over a network, so you can sit at one
+computer and give commands to another one, or even to more than one.
+
+SSH, Telnet and Rlogin are \i\e{network protocols} that allow you to
+do this. On the computer you sit at, you run a \i\e{client}, which
+makes a network connection to the other computer (the \i\e{server}).
+The network connection carries your keystrokes and commands from the
+client to the server, and carries the server's responses back to
+you.
+
+These protocols can also be used for other types of keyboard-based
+interactive session. In particular, there are a lot of bulletin
+boards, \i{talker systems} and \i{MUDs} (Multi-User Dungeons) which support
+access using Telnet. There are even a few that support SSH.
+
+You might want to use SSH, Telnet or Rlogin if:
+
+\b you have an account on a Unix or VMS system which you want to be
+able to access from somewhere else
+
+\b your Internet Service Provider provides you with a login account
+on a \i{web server}. (This might also be known as a \i\e{shell account}.
+A \e{shell} is the program that runs on the server and interprets
+your commands for you.)
+
+\b you want to use a \i{bulletin board system}, talker or MUD which can
+be accessed using Telnet.
+
+You probably do \e{not} want to use SSH, Telnet or Rlogin if:
+
+\b you only use Windows. Windows computers have their own
+ways of networking between themselves, and unless you are doing
+something fairly unusual, you will not need to use any of these
+remote login protocols.
+
+\H{which-one} How do SSH, Telnet and Rlogin differ?
+
+This list summarises some of the \i{differences between SSH, Telnet
+and Rlogin}.
+
+\b SSH (which stands for \q{\i{secure shell}}) is a recently designed,
+high-security protocol. It uses strong cryptography to protect your
+connection against eavesdropping, hijacking and other attacks. Telnet
+and Rlogin are both older protocols offering minimal security.
+
+\b SSH and Rlogin both allow you to \I{passwordless login}log in to the
+server without having to type a password. (Rlogin's method of doing this is
+insecure, and can allow an attacker to access your account on the
+server. SSH's method is much more secure, and typically breaking the
+security requires the attacker to have gained access to your actual
+client machine.)
+
+\b SSH allows you to connect to the server and automatically send a
+command, so that the server will run that command and then
+disconnect. So you can use it in automated processing.
 
-\# Section on `what is Telnet? what is SSH?' for the people who
-\# don't have the first clue what they are. Explain what they're
-\# good for and why you might want to use one, and explain under
-\# what conditions you might _not_ want to use one.
+The Internet is a hostile environment and security is everybody's
+responsibility. If you are connecting across the open Internet, then
+we recommend you use SSH. If the server you want to connect to
+doesn't support SSH, it might be worth trying to persuade the
+administrator to install it.
 
-\# Section on `what's the difference between Telnet and SSH?' where
-\# we evangelise - POLITELY! - about SSH and security
+If your client and server are both behind the same (good) firewall,
+it is more likely to be safe to use Telnet or Rlogin, but we still
+recommend you use SSH.