what is firewall

firewall Last modified: Thursday, August 26, 2004





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(fīr´wâl) (n.) A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
There are several types of firewall techniques:

Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.
Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.
In practice, many firewalls use two or more of these techniques in concert.

A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.



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For internet.com pages about firewall . Also check out the following links!




eSecurity Planet
A resource for daily information on e-security targeted to IT managers. The site provides users with information from a variety of sources, including experts at security product and services firms, and the consultants who follow the security industry.


Design the Firewall System
A practice from the CERT Security Improvement Modules.


Extinguishing Firewall Hyperbole
Are new firewall technologies improvements or complications? Evaluate the pros and cons.


Firewall Info
Protect your system with a firewall. You must protect your system with a personal firewall, especially if you are using DSL or cable modem.


Firewalls FAQ
Contains answers to basic questions about firewalls.


Great Walls of Fire
Hackers, lurking cyber punks and viruses. Enough to give any network administrator the willies. But, an efficient firewall could be just the armor your network may need to combat most of these threats.(2001)


SecurityTracker.com
Information on the latest security vulnerabilities, free SecurityTracker Alerts, and customized vulnerability notification services.


Why You Need a Firewall
Describes security issues when connecting to the Internet, with information on how to protect your network. This page is hosted by Cisco Systems Inc.


Yahoo!'s firewall companies page
Yahoo!'s directory of firewall companies.


Yahoo!'s firewalls page
Yahoo!'s directory of firewalls.



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Nokia Security Products at SecureHQ - Authorized reseller of the complete line with great prices. Fast shipping. Pre-bid Federal pricing available via our NASA SEWP contract.


Business Computing
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application gateway
bastion host

bit bucket

DMZ

extranet

firewalking

intranet

IP spoofing

NAT

network

packet filtering

PIX Firewall

port scanning

proxy server

pulsing zombie

security

stateful inspection

TCB

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