Question

Up until now, all the tools discussed are embedded in your operating systems. This tool will require a little more effort on your part. PuTTY is a free, open‐source terminal emulation, serial console, and network file transfer program. Originally written for Windows, it has evolved to be used with other operating systems. PuTTY is an amazingly versatile tool that allows you to gain secure remote access to another computer and is most likely the most highly used SSH client for the Microsoft Windows platform.

I believe that many IT professionals who have been in the industry for a while lose track of where we have been. We keep adding knowledge and experience and expertise to our repertoire and think, “Everyone should know that.” As an educator, I am not allowed to do that. It's my job to show you how to use all these new shiny things in your toolbox. I can hear some people saying, “You had me until SSH!”

Secure Shell (SSH) is a network protocol for creating an encrypted channel over an unencrypted network. The Internet is way unsecured. You don't want your data out there in the World Wide Web dangling freely for all to see! SSH provides a computer administrator with a safe way to reach a system that is remote using strong authentication and secure, encrypted data transmission. There have been times as an administrator when part of my responsibilities were to manage computers I could not reach out and physically touch—execute commands or move files from one computer to another. SSH is the protocol most hosts support. An SSH server, by default, will listen on TCP port 22.

As I mentioned earlier in this chapter, SSH creates an encrypted channel to communicate over. The first version of SSH debuted in 1995. Brad Pitt was the Sexiest Man Alive, Mel Gibson's Braveheart won Best Picture, and Match.com was new and the only online dating site. A lot…and I mean a lot has changed since then. Over the years, several flaws were found in SSH1, and it is no longer used. The current SSH2 was adopted in 2006 and uses a stronger encryption algorithm to improve security. As of yet, there are no known exploitable vulnerabilities in SSH2, although there have been rumors that the National Security Agency (NSA) may be able to decrypt some SSH2 traffic.

In Lab 1.6 , you'll use PuTTY.

---

LAB 1.6 : PuTTY

1. You can download a copy of PuTTY from www.putty.org . There will be a link on the page that takes you to the package file. Make sure you are getting the correct version for the hardware you are running. One size does not fit all.
2. Double‐click the file you just downloaded. Follow the instructions until you finish the installation and then open PuTTY by double‐clicking the icon that looks like two old computers linked together with a lightning bolt.

   When the software starts, a PuTTY Configuration window should open, such as what you see in Figure 1.10 . The window pane on the left side lists the categories: Session, Terminal, Window, and Connection. The right side of the window will change depending on what category you have selected on the left.

   

   Figure 1.10 : PuTTY Configuration window

3. In the Session view, enter the domain name or IP address you want to connect to. Port 22 specifies that you will be using SSH. The Connection Type setting lets you choose one of the following options:
   • Raw : This is usually used by developers for testing.
   • Telnet : Telnet is no longer secure. Passwords are sent in clear text. This is a bad idea.
   • Rlogin : This is legacy, which means old (like 1982 old). It uses port 513 and only connects Unix to Unix. Ignore it.
   • SSH : This is the protocol most hosts support. An SSH server, by default, will listen on TCP port 22.
   • Serial : This is used for controlling some physical machinery or communication devices.
4. After you have supplied the IP or domain address, you should get a terminal window, which will ask for your credentials. If you are able to supply them, you will have a command‐line terminal on the machine you just accessed. Some useful commands include the following:

   pwd	Present working directory
   cd	Change directory
   cd ~	Go to the home folder
   ls	List files
   ls –h	List files with the size
   cp	Copy a file
   cp –r	Copy a folder with all the files inside
   mv	Move a file
   mkdir	Make a directory
   rm	Delete a file

   The session will terminate when you press Ctrl+D.

---

---

NOTE

The first time you connect another system, you may be prompted to accept the server's SSH key or certificate. It might have some wording like “The server's host key is not cached in the registry.” You see an example in Figure 1.11 . This is normal. When you click Yes, you are establishing trust between the two hosts.

Figure 1.11 : PuTTY security alert

---

I truly hope that I have given you a foundation to start to build on and that you have added these tools to your cybersecurity toolkit. Some of these tools may have just been a review for you, and some of them might have been new. These tools will help you not only with troubleshooting networks but with securing them as well.