Firewall

From Saferpedia

A firewall is part of a computer system or network designed to block unauthorized access. It is a device or ensemble of devices configured to allow, deny, encrypt, decrypt traffic between computers from different areas of security based on a set of rules and criteria. Firewalls may be either hardware or software or a combination of both.

Firewalls are frequently used to stop unauthorized users to access private networks, especially Intranet networks. All messages incoming or outgoing pass trough a firewall; it exams each message and blocks those not meeting specific security criteria.

There are several kinds of firewall techniques:

1. Package filter: inspects each package passing trough network and accepts or rejects them based on user defined rules. Although it is difficult to configure is quite efficient and transparent for user. It is sensible instead to fake IP addresses.
2. Gateway applications:security mechanisms are applied for specific applications like FTP servers and Telnet. This is very efficient but it may lead to a decrease of performances;
3. Circuit Level Gateway: security mechanisms are applied when a TCP or UDP connection it's established. Once the connection was established the package flow between hosts may be realized without verification;
4. Proxy server: intercepts all incoming and outgoing messages in the network. The proxy server hides the real network address.

Functionality

A firewall is a dedicated software, or a software running on a computer inspecting network traffic passing trough and rejecting packages based on a set of rules.

It is also a software or hardware that usually is placed between a protected network and a unprotected one and it acts like a protection gate ensuring that nothing private comes out and nothing bad comes in.

The main task of a firewall is to control the traffic flow between computer networks with different levels of trust. A typical example is Internet, an area not trusted and a trusted internal network often mentioned as being a perimeter network or demilitarized zone (DMZ).

A firewall functionality inside a network is like a physic firewall with fire doors from the civil building area.

History

Firewall technology appeared at the end of 1980 when internet was a quite new technology regarding worldwide connectivity and use. Firewall's predecessors for network security were routers used at the end of 1980 for separated networks.

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