Firewall

Definitions: Firewall

Firewall

Noun

1. (informal) the application of maximum thrust; "he slammed the throttle to the firewall".

2. Fireproof (or fire-resistant) wall designed to prevent the spread of fire through a building.

Specialty Definitions: Firewall

Domain	Definitions
Computing	Firewall 1. firewall code. 2. firewall machine. Source: The Free On-line Dictionary of Computing.
Energy	A wall to prevent the spread of fire; usually made of non-combustible material. (references)
Source: compiled by the editor from various references; see credits.

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Specialty Definition: Firewall

(From Wikipedia, the free Encyclopedia)

Construction

In the traditional meaning, a firewall is simply a windowless, non-flammable wall (or a wall of substantially heavier construction than other walls in the building) built to prevent fire from spreading beyond one section of a building. Such firewalls form the built-up equivalent of firebreaks in a landscape.

Computer Networking

By extension, the computing world uses the term firewall for a piece of hardware or software put on the network to prevent some communications forbidden by the network policy.

A major distinction separates:

a Personal firewall - a software application which normally filters traffic entering or leaving a single computer, and
a traditional Firewall, normally running on a dedicated network device or computer positioned on the boundary of two or more networks or DMZs (Demilitarized zones). Such a firewall filters all traffic entering or leaving the connected networks.

The latter definition is the conventional meaning of "firewall": the remainder of this article addresses such traditional firewalls.

Firewalls (in the sense of computer networking devices) come in several categories and sub-categories. They have the basic task of preventing intrusion from a connected network -- but they try to accomplish this in varing ways. Distinguish two major categories of firewalls:

network layer firewalls
application layer firewalls.

These two types of firewall may overlap; indeed single systems have implemented both together.

Network layer firewalls operate at a (relatively low) level of the TCP/IP protocol stack as IP-packet filters, not allowing packets to pass the firewall unless they meet the rules defined by the firewall administrator or applied by default (as in some inflexible firewall systems). A more permissive setup could allow any packet to pass the filter as long as it does not match one or more "negative-rules", or "deny rules".

Application layer firewalls work on the application level (i.e., all browser traffic, or all telnet or ftp traffic), and may intercept all packets traveling to or from an application. They block other packets (usually dropping them without acknowledgement to the sender). In principle, application firewalls can prevent all unwanted outside traffic from reaching protected machines. By inspecting all packets for improper content, firewalls can even prevent the spread of such things as viruses. However, in practice, this become complex, and would become so difficult to attempt (given the variety of applications and the diversity of content each may allow in its packet traffic) that comprehensive firewall design does not generally attempt this approach.

A proxy device (running either on dedicated hardware or as software on a general purpose machine) may act as a firewall by responding to input packets (eg, connection requests) in the manner of an application, whilst blocking other packets.

Proxies make tampering with an internal system from the external network more difficult, and misuse of one of its internal systems would not necessarily cause a security breach exploitable from outside the firewall (as long as the application proxy remains intact and properly configured). Conversely, intruders may hijack a publicly-reachable system and use it as a proxy for their own purposes; the proxy then masquerades as that system as far as others are concerned. While use of internal address spaces enhances security, hackers may still employ methods such as IP spoofing to attempt to pass packets to the target internal network.

Firewalls often have network address translation functionality, and the hosts protected behind a firewall commonly use so-called "private address space", as defined in RFC 1918. Administrators often set up such scenarios in a effort (of debatable effectiveness) to disguise the internal address or network.

Proper configuration of firewalls demands skill. It requires considerable understanding of network protocols and of computer security. Small mistakes can render a firewall worthless as a security tool. Faith in misconfigured firewalls is misplaced indeed.

Also see: stateful firewall, stateless firewall, end-to-end connectivity

External links

Matt Curtin and Marcus J. Ranum, Internet Firewalls: Frequently Asked Questions: http://www.faqs.org/faqs/firewalls-faq/

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Firewall."

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Crosswords: Firewall

Specialty definitions using "firewall": DMZ ♦ extranet ♦ firewall code, firewall machine ♦ iron box ♦ proxy gateway, proxy server ♦ rust proofer ♦ SOCKS ♦ UNDERCOATER ♦ Venus flytrap, Virtual Private Network ♦ wild side. (references)

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Modern Usage: Firewall

Domain	Usage
Screenplays	Enough! Breach this firewall with your viral energies or suffer! (ReBoot; writing credit: Christy Marx; Mark Leiren-Young)
Source: compiled by the editor from various references; see credits.

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Commercial Usage: Firewall

Domain	Title
Books	CCSP Cisco Secure PIX Firewall Advanced Exam Certification Guide (CSSP Self-Study) (reference) Cisco Secure Pix Firewall Fundamentals [DOWNLOAD: PDF] (reference) Firewall (reference) Firewall Architecture for the Enterprise (reference) (more book examples)

High Tech	D-Link DI-704 Internet Gateway and Firewall with 4 Port Switch (reference) Netgear FVS318NA VPN Firewall Router with 8-Port Switch (reference) SuSE Linux Firewall (reference) (more camera examples; more video game examples; more computer examples; more electronic examples; more software examples)
Source: compiled by the editor from various references; see credits.

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Non-Fiction Usage: Firewall

Subject	Topic	Quote
Business		Practically all firewall software vendors mentioned above offer VPN solutions. (references)
		The network is protected by a sophisticated firewall, which guarantees confidentiality. (references)
		There are some free firewall software in use that can be freely downloaded such under GNU public license such as LINUX. (references)
Travel	Vietnam	Vietnam has an extensive and cumbersome firewall system that limits some access to outside sites and prohibits most use of wide area networks. (references)
Source: compiled by the editor from ICON Group International, Inc.; see credits.

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Usage Frequency: Firewall

"Firewall" is generally used as a noun (singular) -- approximately 100.00% of the time. "Firewall" is used about 3 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted)

Parts of Speech	Percent	Usage per 100 Million Words	Rank in English
Noun (singular)	100%	3	202,518

Source: compiled by the editor from several corpora; see credits.

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Expressions: Firewall

Expressions using "firewall": firewall code ♦ firewall machine. Additional references.
Source: compiled by the editor from various references; see credits.

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Frequency of Internet Keywords: Firewall

The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com.

Expression	Frequency per Day	Expression	Frequency per Day
firewall	13,383	mcafee firewall	129
free firewall	1,728	best firewall	125
personal firewall	580	firewall outpost	116
firewall software	524	internet firewall	111
norton firewall	436	free firewall downloads	111
tiny personal firewall	318	firewall free ware	109
test firewall	270	black ice firewall	101
norton personal firewall	236	firewall zone alarm	97
sygate personal firewall	231	free personal firewall	94
firewall hardware	215	firewall review	83
firewall free download	209	norton personal firewall 2003	79
sygate firewall	205	pix firewall	77
tiny firewall	195	computer firewall	76
firewall protection	182	firewall appliance	75
curriculum cv firewall ip manager program resume rsum security tcp vitae	181	window xp firewall	71
conseal pc firewall	164	router firewall	68
firewall download	160	checkpoint firewall	68
firewall security	157	network firewall	64
free firewall software	146	bypass firewall	63
linux firewall	141	xp firewall	62
Source: compiled by the editor from various references; see credits.

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Modern Translations: Firewall

Language		Translations for "firewall"; alternative meanings/domain in parentheses.
Chinese		防火墙, 火牆 . (various references)

Danish		brandskot (fire wall). (various references)

Dutch		firewall, brandscherm (flame arresting). (various references)

Finnish		palomuuri (fire wall, fire-proof wall, party wall). (various references)

French		firewall, pare-feu (fire shield, firebreak), mur pare-feu, cloison pare-feu (fire wall). (various references)

German		Firewall, Feuerschutzwand. (various references)

Greek		αντιπυρικό τοίχωμα. (various references)

Hungarian		tûzfal. (various references)

Italian		parete antincendio. (various references)

Japanese Kanji		防火壁 , フーゼル油 (far, Far East, farce, farm, farm stay, fast, fast back, fast break, fast food, fiber, fiberboard, fiberglass, fiberscope, fibre, fight, fight money, fighter, fighting spirit, file, filename, filesystem, filing system, final, final set, finance, fire, fire alarm, fire insurance, fire storm, fireman, fireproof, firm, firm banking, firmware, first, first impression, first lady, first run, first-class, first-name, five-star, food, food processor, Fourier, fur, fur coat, furniture, fusel oil, hood, hoop, pharmacy, purse, whodunit). (various references)

Japanese Katakana		ファイアーウオール , ぼうかへき. (various references)

Korean		방호벽. (various references)

Pig Latin		irewallfay

Portuguese		divisão guarda-fogo, corta-fogo (fireguard). (various references)

Spanish		mampara cortafuegos. (various references)
Source: compiled by the editor from various translation references.

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Derivations & Misspellings: Firewall

Derivations
	Words beginning with "firewall": firewalled, firewalling, firewalls. (additional references)
Misspellings
	"Firewall" is suggested in spellcheckers for the following: firehall, firewell. (additional references)
Source: compiled by the editor, based on several corpora (additional references).

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Anagrams: Firewall

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "a-e-f-i-l-l-r-w"
	-1 letter: flawier.
	-2 letters: faille, faller, ferial, filler, refall, refill, wailer, wallie, willer.
	-3 letters: afire, ariel, farle, fella, feral, feria, filar, filer, fille, flail, flair, flare, flier, frail, frill, ileal, iller, lifer, rifle, rille, wafer, waler.
	-4 letters: alef, alif, aril, earl, fail, fair, fall, fare, farl, feal, fear, fell, fiar, fila, file, fill, fire, flaw, flea.
	Words containing the letters "a-e-f-i-l-l-r-w"
	+1 letter: firewalls.
	+2 letters: firewalled, wearifully.
	+3 letters: cauliflower, farewelling, firewalling.
	+4 letters: cauliflowers.
	+5 letters: caulifloweret.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.