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Firewalls

Firewalls are your computer's sentinels, guardians, defenders, all rolled into one.

Semi technically speaking, A firewall is a system or a group of many systems that controls the exchange of data across machines or networks. It enforces a permit/deny policy that is determined by the system's administrator.

As the Internet expands, so does it's abuse and misuse. After all, the Internet is nothing but a network of computers and it is possible to access another machine on the computer just like you could enter anyone's house provided you had the keys (authorized access) or did not have the keys. (break in). Of course there are times when the house owner will leave the house unlocked, which makes entry not only easy, but inviting.

A firewall is the front line tool that will guard your computer against unscrupulous visitors while ensuring that you are able to continue your work uninhibited. From large organizations to home users, anyone who would like their data to remain private and unaffected by viruses and other Malaware would need a firewall in place.

Firewalls can be configured to do various things. Some may be configured do allow only email traffic, while some may block access via certain ports. Still some may block all traffic from the outside world to the inside or heavily monitor it, while allowing unrestricted internal communication. Firewalls also act like a sign in book where all incoming and outgoing data is logged. This enables the administrators to keep a check on potentially threatening traffic and who was trying to gain unauthorized access.

But a firewall is only as good as the overall system and infrastructure it is built to protect. A very efficient firewall with other security holes, is like having a concrete wall on 3 sides but a wooden fence on the 4 th. It will not protect you, if your security polices are not consistent and flawless.

Firewalls will also be ineffective against individuals who will bypass the system in order to cause damage to the organization or the system. Sensitive data can also be carried out in removable media which the firewall has no control over.

Basically there are 3 types of firewalls

1. Network Layer firewalls

2. Application Layer firewalls

3. Hybrid firewalls

Network layer firewalls usually work at a relatively low level as a packet filter whose basic job is to decide which packets will pass through the system depending on the rules set by the administrator. These firewalls operate very fast as they work on a low level.

Such firewalls can be divided into two types. Stateful and Stateless Firewalls. Stateful firewalls contain information about the state of the connections as part of their rules whereas stateless firewalls do not have any complex decision making capabilities. Stateless firewalls are less secure than the Stateful ones.

Application Layer Firewalls work on the application level of the TCP/IP stack and intercept all packages traveling to and fro an application. As they inspect all packets for improper content, they have the potential to prevent viruses from entering the system. A proxy device can act as a application layer firewall as it responds to input packets just as an application would and rejecting the other packets.

Hybrid firewalls attempt to encompass the features of both; Application layer security as well as packet filtering. The advantage of such an architecture is that is adapts to the requirement at that particular time and provides the necessary checks.

Firewalls are a necessity now, not only for organizations and corporations but also for home users due to the increasing large number of viruses and worms that crawl the network.

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