Firewall

A Firewall controls communication between network segments, commonly used to protect internal networks from unwanted actions from external networks. It controls traffics by deny, permit, etc. based on type of protocols on specified direction, for example deny FTP from Internet. Typically a firewall is placed in between the Internet and an organization's internal network, or between the Internet and a DMZ or DMZ and an internal network. Firewalls are carefully configured to prevent loss or disruption of organizations data or applications. A firewall can be a hardware appliance such as a Cisco ASA, PIX, SonicWALL, WatchGuard or Juniper NetScreen etc; or a software package running on a computer, such as an ISA Server of iptables.

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