Introduction to Firewall

Firewall is a first line of defense and protective barrier between your network and the outer world.  It can be a software or hardware and it is configured and attached with the gateway computer.  It encrypts, filters, monitors, permits or denies all the network traffic.  A system without the implementation of the firewall can easily be attacked by the viruses, hackers, intruders, unauthorized access and other internal and external threats.  It regulates the traffic between the computer network and the internet.  It protects the resources of the private network from the internal and external threats.

Windows XP Professional has built-in firewall software that allows the users to filter the incoming and outgoing traffic by applying different rules.  The rules can be based on the IP addresses of the source and destination, port number, domain names and specific applications and protocols such as FTP, HTTP, Remote desktop, Telnet, SMTP, POP3 and Https etc. A firewall works closely with the router and many routers has the built-in firewall.  The common functionalities include packet filtering, application gateway, proxy server and circuit relay.

Firewall Features

The common features of a firewall program include the following.

Packet filtering
Ports blocking and scanning
Web filtering
URL Screening
Web caching
User blocking
Domain blocking
Antivirus
Spam Filtering
Email Scanning
Network Access Rules
Network Address Translation (NAT)
User Authentication
Intrusion Protection
Network Activity Monitoring

Types of Firewall

Firewall can be categorized into the following two major categories.

Software Firewall

There are many software firewall products that are usually installed and configured on the Server computer.  The most common software firewall includes Zone Alarm, Wingate, Barracuda spam firewall, Symantec Norton Personal Firewall, McAfee Personal Firewall Plus and Sygate® Personal Firewall PRO.

Hardware Firewall

A hardware firewall is a dedicated device that is usually attached with the gateway computer. Many routers provide have built-in firewall features.  It filters the network traffic and blocks the unwanted traffic.