Secure Shell (SSH) is a secure version of Telnet that you can use to log on and open a command line on a remote machine. You can also use SSH to establish an encrypted tunnel between two machines, effectively creating a VPN. Different versions of SSH use RSA or Digital Signature Algorithm (DSA) for secure key exchange and 3DES or Blowfish for data encryption. You can use a free program such as Stunnel (http://www.stunnel.org) along with a free version of SSH such as OpenSSH (http://www.openssh.org) to tunnel protocols such as Web and mail protocols through an encrypted SSH tunnel. All you need is a machine at either end running both these programs. SSH and Stunnel are an inexpensive way to implement a VPN, although setting up such a VPN requires a lot of configuration and might not scale to handle a large number of machines. An SSH VPN can, however, make a nice solution for connecting two servers that need to communicate securely, such as a Web server and a back-end database server.
A VPN can protect your devices, including desktop computer, laptop, tablet, and smart phone from prying eyes. Your devices can be prime targets for cybercriminals when you access the internet, especially if you’re on a public Wi-Fi network. In short, a VPN helps protect the data you send and receive on your devices so hackers won’t be able to watch your every move.
In very simple terms, a VPN connects your PC, smartphone, or tablet to another computer (called a server) somewhere on the internet, and allows you to browse the internet using that computer’s internet connection. So if that server is in a different country, it will appear as if you are coming from that country, and you can potentially access things that you couldn’t normally.