Short for Virtual Private Network, a VPN is a network that is constructed by using public wires to connect nodes. VPN technology allows disparate networks to communicate securely with each other typically by way of the public Internet.

In a traditional implementation, a firewall or other security device that provides data encryption and other security mechanisms is installed at each physical office location and configured to communicate via the VPN over the public Internet with appropriate peer devices. Traffic sent over the VPN is encrypted per the specified security policy.