Intranet and Extranet An Intranet is a corporate LAN that uses Internet technology and is secured behind a company’s firewall. Links various servers, clients, databases and applications. Access to intranets is usually strictly controlled within a corporate group. Intranets are most often found in (Ranked in order of most common use) --Banks -- IT companies -- Manufacturing companies --Large retail companies -- Service companies (ie, Travel. Hotel) An Extranet (extended intranet) uses TCP/IP protocol to link intranets over the public Internet.  Many Extranets have protected areas “Virtually Private Networks”.  Access to Extranets is quite open and allows for independent groups to collaborate usually parts suppliers to a big manufacturer.  Extranets are most often found in (Rank in order of most common use) -- IT services -- Computer companies (hardware) -- Financial services -- Travel -- Manufacturing -- Professional services -- Real estate