Information on Firewalls

A firewall is a combination of special purpose programs and special devices that are used to control the traffic flow in and out of a network and also prevent unauthorized access of computer data by intruders or by the host users. The word firewall was coined from the physical firewalls that are used to prevent fires spreading in buildings. A firewall works under some guidance and rules that are defined by the system administrator who may provide a list of network sites to the firewall that the firewall should block. Certain keywords may also be quoted on the firewall program that may serve as checks that may be used to filter out blocked sites.

Areas that firewalls may be used
 Home computers
 Intranets
 Network servers
 Portable devices like mobile phones and pdas

How do firewalls work?

The general idea of a firewall is to regulate traffic flow from one computer network to another. It may prevent networks from being intruded if they are well configured. Data that is quantized as packets comes to the firewall and is scanned to see if there are any keywords or data from any restricted sites. The firewall thus prevents this data from going into the system or private network.

There are various types of firewalls
 Packet filtering firewalls-This scrutinizes data packets that come through the network to decide whether they are allowed or to be rejected. Upon rejection, a message is sent back to its sender to inform him that the sent data has been dropped. Routers are used for this purpose.
 Application proxy firewalls-This firewall handles communication between applications in the host computer and the outside world. Communication signals by the applications are first handled by the firewall and then the firewalls send the signals to the targetted system in the outside world.
 Stateful filters- This is a specialized class of firewalls. It keeps a list of all the connections passing through the firewall and with this, it is possible to determine whether a packet is part of an existing connection or a new connection.

Advantages of firewalls
 Relatively inexpensive or free for personal use.
 New releases are becoming user friendly.
 You can monitor incoming and outgoing security alerts and the firewall company will record and track down an intrusion attempt depending on the severity.
 Some firewalls but not all can detect viruses, worms, Trojan horses, or data collectors.
 All firewalls can be tested for effectiveness by using products that test for leaks or probe for open ports.

Disadvantages of firewalls
 "Always on" connections created by Cable and DSL connections create major problems for firewalls. They expose protected networks hence this may attract intruders.
 Firewalls cannot protect from internal sabotage within a network or from allowing other users access to your PC.
 Firewalls cannot edit illicit material like pornography, violence, drugs and bad language. This would require you to adjust your browser security options or purchase special software to monitor your children's Internet activity.
 Firewalls offer weak defense from viruses so antiviral software and an IDS (intrusion detection system) which protects against Trojans and port scans should also complement your firewall in the layering defense.
 Some firewalls claim full firewall capability when it's not the case. Not all firewalls are created equally or offer the same protection so it's up to the user to do their homework.
 Cost varies. There are some great free firewalls available to the PC User but there are also a few highly recommended products, which can only be purchased. The difference may be just the amount of support or features that a User can get from a free product as opposed to a paid one and how much support that user thinks he or she will require.
 There have been claims made by IDS (Intrusion Detection System) companies where Trojan's were detected which disabled certain Firewalls programs thus leaving the PC vulnerable to malicious actions.