"An Extranet is a collaborative network that uses Internet Technology to link businesses with their suppliers, customers or other businesses that share common goals. An Extranet can be viewed as part of a company's Intranet that is made accessible to other companies or that it is a collaboration with other companies.
An Extranet would seem to require a degree of security and privacy from competitors. It also might be viewed as an intersection set of a number of different company Intranets.
Security and privacy could be obtained either by ensuring that transmission lines were privately owned or leased, by tunneling through the Internet, or by using the Internet with special forms of security protection and password authorization."