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In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed to not be secure or trusted. Firewalls are often categorized as either ''network firewalls'' or ''host-based firewalls''. Network firewalls are a software appliance running on general purpose hardware or hardware-based firewall computer appliances that filter traffic between two or more networks. Host-based firewalls provide a layer of software on one host that controls network traffic in and out of that single machine. Routers that pass data between networks contain firewall components and can often perform basic routing functions as well,〔(【引用サイトリンク】title= What is Firewall? )〕〔Definition of (Firewall ), Check Point Resources〕 Firewall appliances may also offer other functionality to the internal network they protect such as acting as a DHCP or VPN server for that network. == History == The term ''firewall'' originally referred to a wall intended to confine a fire or potential fire within a building. Later uses refer to similar structures, such as the metal sheet separating the engine compartment of a vehicle or aircraft from the passenger compartment. Firewall technology emerged in the late 1980s when the Internet was a fairly new technology in terms of its global use and connectivity.The predecessors to firewalls for network security were the routers used in the late 1980s: * Clifford Stoll's discovery of German spies tampering with his system〔 * Bill Cheswick's "Evening with Berferd" 1992, in which he set up a simple electronic "jail" to observe an attacker〔 * In 1988, an employee at the NASA Ames Research Center in California sent a memo by email to his colleagues〔() Firewalls by Dr.Talal Alkharobi〕 that read, "We are currently under attack from an Internet VIRUS! It has hit Berkeley, UC San Diego, Lawrence Livermore, Stanford, and NASA Ames." * The Morris Worm spread itself through multiple vulnerabilities in the machines of the time. Although it was not malicious in intent, the Morris Worm was the first large scale attack on Internet security; the online community was neither expecting an attack nor prepared to deal with one.〔(RFC 1135 The Helminthiasis of the Internet )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Firewall (computing)」の詳細全文を読む スポンサード リンク
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