• Explanation 1: Tunnelblick is a program that can be used to securely connect a Mac running OS X to an OpenVPN server. The server then connects the Mac to a remote network or to the Internet, bypassing untrusted networks, censorship, and eavesdropping.

It does this by creating a "Virtual Private Network", or "VPN [wiktionary.org]", to the OpenVPN server using a program named "OpenVPN", which is included within the Tunnelblick application. When you connect through a VPN, your computer sends some or all network traffic through a "tunnel" to the VPN server, which then passes on your network traffic to a local network or the Internet. It is as if you were connecting to the network or Internet through the VPN server instead of your computer. Normally, all traffic between your computer and the VPN server is encrypted.

VPNs are primarily used for three purposes (sometimes all three simultaneously):

• To securely connect a computer to the Internet, even though it may be connecting through an untrusted network (a wireless network at a hotel or airport, for example);
• To securely connect a computer to the Internet as if it were located somewhere else (connect a computer in the USA as if it were located in the UK so that BBC content may be accessed, for example); and
• To securely connect a computer to a company's internal network or some part of it (a branch office, for example).

In addition to Tunnelblick, you need access to a VPN server. Your company may provide one, or you can obtain VPN service from any of several VPN service providers, or you can use another one of your computers or a router to act as a VPN server. See Getting VPN Service for details.

• Explanation 2: Tunnelblick is a ready-to-use Graphic User Interface (GUI) for OpenVPN on Mac OS X. It provides easy-to-use control of OpenVPN server and/or client connections.

It runs on OS X 10.4 through 10.7 (Tiger, Leopard, Snow Leopard, and Lion). It comes as a ready-to-use Universal application with all necessary binaries and drivers (including OpenVPN and tun/tap) included. No additional installation is necessary -- just add your configuration and encryption information.

Tunnelblick is free software licensed under the GNU General Public License (GPL) Version 2.

PLEASE USE THE TUNNELBLICK DISCUSSION GROUP FOR COMMENTS OR QUESTIONS