Securing Windows NT/2000 Servers for the Internet

Open Source (SSH, Cygwin, TCP Wrappers, and VNC)

This section describes the third remote administration solution—one that is based on a variety of freely available components.

Getting Started with the Secure Shell

The Secure Shell (SSH) is a suite of programs that allows a user to log on to, or execute commands on, another computer over the network. SSH also allows copying files from and to a remote host. This is all done in a secure manner — hence the name Secure Shell. SSH is intended as a replacement for the notoriously unsecure Berkeley “r” commands: rlogin , rsh/remsh , and rcp.

There are SSH implementations available for many platforms. These implementations allow, for example, accessing the Windows NT command prompt from a computer running Unix or vice versa. They even allow getting a remote Windows NT graphics console with mouse and keyboard in a secure manner from a Unix box; I describe this later, in Section 4.3.6.”

SSH was developed by Tatu Ylönen. Originally it was free software, but after Version 1.2.12 the license was made more restrictive. The current reference implementations of SSH can’t be used for commercial use without getting a license from Datafellows (http://www.datafellows.com/ ). Another problem with the reference implementations is that they use patented algorithms like IDEA and the RSA cryptosystem (but note that RSA’s U.S. patent expired on September 20, 2000); see Section 1.5 in Chapter 1 for a summary of cryptographic algorithms commonly used in Windows ...