SSH - Secure Shell was originally developed for UNIX by Tatu Ylonen. The first version implemented a simple RSA based transport layer encryption system. It was oriented towards users of the "rcmd" suite of utilities. Conceptually it is similar to SSL but it uses uncertified RSA public keys. The client and server have config files with the keys in them. One advantage when compared with SSL is that SSH compresses the data stream prior to encyption. SSH can multiplex the data stream, this can be used to run several virtual sessions under one TCP connection. In other words, you can think of this as a secure VPN, Virtual Private Network.It can facilitate secure "X" sessions, or be used to tunnel multiple protocols through a firewall.
SecureCRT is a commerical product available at no charge to members of the MIT community. The MIT distribution can be found at http://web.mit.edu/software/win.html.
This software is for use of MIT faculty, staff, and students only. Information Systems thanks the MIT Media Lab for making this product available to the MIT community.
WARNING: SecureCRT is available only in the United States and Canada. SecureCRT is subject to U.S. export control. This software cannot be transmitted, exported, or reexported without written consent of the Bureau of Export Administration, United States Department of Commerce.
The latest release of Cygwin contains OpenSSH, which has both a command-line client (ssh) and command-line server (sshd).
There was a warning posted on NTBugTraq in May of 1998 which may or may not apply to the latest cygwin distribution:
A word of warning when using cygwin for daemons -- cygwin was NOT designed with security in mind, and in particular is not safe in a multi-user environment. Cygwin keeps shared state (ie. the process table) in shared memory that all cygwin processes can access. By modifying shared state you can coerce programs to do things they weren't designed to allow.
What does this mean? If you do use sshd or telnetd or some other daemon compiled with cygwin, don't allow more than one account to use it, or if you do, realize that cygwin doesn't enforce security between the accounts."
Using SSH in conjunction with VNC allows NT machines to be managed remotely using a GUI interface in a secure manner. Since VNC is available on a number of platforms an NT machine is not required for the remote management. This combination can also be used to securely manage a remote UNIX machine from an NT machine.
PuTTY is a free, open source Win32 Telnet/SSH client. Source code and binaries are available at http://www.chiark.greenend.org.uk/~sgtatham/putty.html.
TTSSH is a free extension to the freeware Tera Term terminal emulator that implements the SSH protocol. It is available at http://www.zip.com.au/~roca/ttssh.html
F-Secure SSH is a commerical version of SSH from Data Fellows. Data Fellows has several products and support a variety of operating systems: http://www.datafellows.com/
Freely available command line versions of SCP and SSH. This page also includes other useful utilities: http://bmrc.berkeley.edu/people/chaffee/winntutil.html
Freely available ssh client for Microsoft operating systems by Cedomir Igaly: The original page at Imperial College appears to be gone. The ssh link at his current home page says: "This free program is not supported any more". However, there is an archived copy of his page at http://uncle-enzo.linuxmafia.com/pub/ms-windows/igaly-ssh/igaly.html. The German mirror listed on that page there contains the binaries, including the 32-bit version.
FiSSH is a secure shell (SSH) and telnet client for Windows developed by Timothy Chen and Doug Mak. It was gifted to MIT for distribution and management of future releases. MIT is distributing both binary and source code free of charge at http://mit.edu/ssh/FiSSH/.
Microsoft Interix (formerly Open NT).
See http://www.lexa.ru/sos/ This page has many other notes about porting code to NT and other Microsoft operating systems (including a NT port of sshd 1.2.26 using cygwin reported to work complete with X11 forwarding).