With the advent of mobile computing, the notion of internal versus external network is no longer physical; intranets and extranets often make use of Virtual private networks (VPN). The main reason for the separation between intranets and the Internet is to preserve the confidentiality and security of the corporate information system. These mini-Internets are owned and managed by companies and enable these corporations to share their resources with their employees without confidential information being made available on the public Internet. Web sites running on an intranet look and act just like any other Web sites, but the firewall surrounding the intranet prevents any unauthorized access thus creating a private web.