Hardware firewalls can be normally bought as a stand-alone product without needing any other devices to function, although there are also hardware firewalls which are already found in broadband routers. A hardware firewall uses packet filtering in testing the header of a packet in order to know its source and destination. The information gathered is then compared to a set of predefined or user-created rules to see if the packet will be allowed to be forwarded or dropped. Generally, hardware firewalls have a minimum of four network ports used to connect other computers. It is important for any computer user to know the specific features of their hardware firewall in order to configure its settings for optimal security.