Intranet

Although firewalls are usually placed between a network and the outside, untrusted network, large companies or organizations often use firewalls to create different subnets of the network, often called an intranet. Intranet firewalls are intended to isolate a particular subnet from the overall corporate network. The reason for the isolation of a network segment might be that certain employees can only access subnets guarded by these firewalls on a need-to-know basis. An example could be a firewall for the payroll or accounting department of an organization. The decision to use an intranet firewall is generally based on the need to make certain information available to some, but not all, internal users, or to provide a high degree of accountability for the access and use of confidential or sensitive information.

Tip: For any systems hosting organization critical applications or providing access to sensitive or confidential information, internal firewalls or filtering routers should be used to provide strong access control and support for auditing and logging.These controls should be used to segment the internal organization network to support the access policies developed by the designated owners of information.