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An SSH tunnel is an encrypted tunnel created through an SSH protocol connection. SSH tunnels may be used to tunnel unencrypted traffic over a network through an encrypted channel. For example, Windows machines can share files using the SMB protocol, which is not encrypted. If you were to mount a Windows filesystem remotely through the Internet, someone snooping on the connection could see your files. To mount the Windows filesystem securely, you can establish an SSH tunnel that routes all SMB traffic to the remote fileserver through an encrypted channel. Even though the SMB protocol itself is unencrypted it is secure because it travels through the encrypted SSH channel.
To create an SSH tunnel, an SSH client is configured to forward a specified local port to a port on the remote machine. Once the SSH tunnel has been established, the user can connect to the specified local port to access the network service. The local port need not be the same as the remote port.
SSH tunnels provide a means to bypass firewalls that prohibit certain Internet services provided that outgoing connections are allowed. For example, an organization may prohibit a user from accessing Internet web pages (port 80) directly without passing through the organization’s proxy filter which provides the organization a means of monitoring and controlling what the user sees through the web. The user may not wish to have their web traffic monitored or blocked by the organization’s proxy filter. If a user is able to connect to an external SSH server, it is possible for them to create an SSH tunnel to forward a given port on their local machine to port 80 on a remote web server. To access the remote web server the user would point their browser to http://localhost/.
Some SSH clients support dynamic port forwarding that allows the user to create a SOCKS 4/5 proxy. The user can configure his/her applications to use their local SOCKS proxy server. This is more flexible than creating an SSH tunnel to a single port as previously described. With SOCKS the user is not limited to connecting only to a predefined remote port and server.
(http://en.wikipedia.org/wiki/Tunneling_protocol#SSH_tunneling)
Before use SSH Tunneling,you must have an SSH account. Next, make sure Putty already installed on your computer. After sure Putty already installed, open Putty. Fill column Host Name (or IP address) with your account ssh host name. Then select SSH at menu. It will be out submenu Tunnels. Click the Tunnels submenu. Fill Source Port with 8080 but you are free to fill it with the numbers only provided that does not collide with any other port. Click Open. Then, you must fill the username and password. After successfully login, minimize Putty and open web browser. Then settings proxy with localhost and port 8080 or your fill number column Source Port on putty. And then, click SOCKS 5. Click OK.
