Firewall 

Firewall

A computer Firewall protects networked computers from intentional hostile intrusion that could compromise confidentiality or result in data corruption or denial of service. It may be a hardware device or a software program running on a secure host computer. In either case, it must have at least two network interfaces, one for the network it is intended to protect, and one for the network it is exposed to. A network firewall sits at the junction point or gateway between the two networks, usually a private network and a public network such as the Internet. The earliest computer firewalls were simple routers. The term "firewall" comes from the fact that by segmenting a network into different physical sub networks, they limited the damage that could spread from one subnet to another - just like fire doors or firewalls.

An Internet firewall examines all traffic routed between your network and the Internet to see if it meets certain criteria. If it does, it is routed between the networks, otherwise it is stopped. A network firewall filters both inbound and outbound traffic. It can also manage public access to private networked resources such as host applications. It can be used to log all attempts to enter the private network and trigger alarms when hostile or unauthorized entry is attempted. Firewalls can filter packets based on their source, destination addresses and port numbers. This is known as address filtering. Firewalls can also filter specific types of network traffic. This is also known as protocol filtering because the decision to forward or reject traffic is dependant upon the protocol used, for example HTTP, ftp or telnet. Firewalls can also filter traffic by packet attribute or state.
There are two access denial methodologies used by computer firewalls. A firewall may allow all traffic through unless it meets certain criteria, or it may deny all traffic unless it meets certain criteria. The type of criteria used to determine whether traffic should be allowed through varies from one type of firewall to another. Computer Firewalls may be concerned with the type of traffic, or with source or destination addresses and ports. They may also use complex rule bases that analyze the application data to determine if the traffic should be allowed through. How a computer firewall determines what traffic to let through depends on which network layer it operates at.

Firewalls protect private local area networks (LANs) from hostile intrusion from the Internet. Consequently, firewall protection allows many LANs to be connected to the Internet where Internet connectivity would otherwise have been too great a risk.

Firewalls allow network administrators to offer access to specific types of Internet services to selected LAN users. This selectivity is an essential part of any information management program, and involves not only protecting private information assets, but also knowing who has access to what. Privileges can be granted according to job description and need rather than on an all-or-nothing basis.



Firewall - Personal Firewall - Firewall Download - Firewall Software - Firewall Protection

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