Your Security & Network System: Firewall

Firewalls are being used to increase the security of a network system. Anyone who is not officially part of the network will be barred from the system. This way, the security of the network is intact and no unnecessary information will leak out from the network. Firewalls also function to grant or deny permission, to encrypt and decrypt or proxy the traffic in the network. A firewall has a set of security rules that it follows to handle the security of the system.

In this video Dr. Soper discusses firewalls and network security. Topics covered include network vulnerabilities, port scanning, network segmentation, firewall security policies, the OSI reference model, packet filtering gateways, stateful inspection firewalls, application proxy gateways, circuit-level gateways, guards, personal firewalls, encryption in the context of network security, network address translation (NAT), and establishing a network security perimeter.




A firewall can be a physical device attached to the computer system or it can be software being run on the computer. It is like a security check where traffic momentarily stops for inspection. If a particular set of traffic contains malicious codes or any other unauthorized processes, the firewall will deny entrance to such kind of traffic. The basic task of any firewall is the regulation of traffic between different computer networks. These networks have different levels of trust based on pre-defined rules. Some computer systems may have no trust while other may have a high level of trust, especially if the network is but internal. Most of the time, there is a middle-level of trust, which has often been referred to as the demilitarized zone. This zone has an intermediate level of trust and it inspects traffic as it passes through and out of the computer network.


Packet Filtering Router

The first generation of firewall devices was referred to as packet filters. This kind of system was developed by the engineers of Digital Equipment Corporation in 1988. This system was very basic but this undertaking was later expanded by the AT&T Bell Labs and other IT engineers. Packet filter routers inspect the “packets” between different computers connected by the Internet. Packets represent the most basic unit of data, which is being transferred between computers connected to the Internet. The packet filtering router has a set of rules. If the packet that seeks entrance to the network matches the set of rules of the router, then it will reject the packet silently or send an error message to the source of the data.

Packet filtering routers or firewalls only look at the packet itself and not into the stream of traffic to which the packet might be connected. As such, this kind of routers does not store any information concerning the state of the connection. Each packet is being screened and analyzed but not the relationships between and among packets. Such a router analyzes, most often, the source of the packet and its destination, the protocol and the port number for UDP and TCP traffic.

The most common protocols being used in communication over the Internet are TCP and UDP. These two protocols use the most popular ports for various kinds of traffic. Because of this, packet filter routers can tell TCP traffic from UDP ones so as to control these kinds of traffic.

Application Gateway / Application Proxy

An application gateway usually uses a proxy server. This then becomes an intermediary that exists between the server and the client. Through the application gateway, a user can easily request for information and data beyond the protected network. In a sense, the application gateway or proxy enforces and takes upon itself some of the security settings of the firewall. An application gateway deals with different kinds of service requests at the application level. Most of the time, application level gateways do have provisions for the World Wide Web and for emails. Each of the supported services in the application gateways is defined. Any services not in the definitions will not be available to users. These definitions should also be applicable to internal hosts. With the communications going to and from the proxy server and the Internet, the proxy server will be considered as the end user instead of the actual user. Because of this, the application level gateway is usually considered as the bastion host with tight security.

At the level of the gateway, access to hard drives is severely limited. This is to prevent any malware or virus from entering the system. Executable files are also prohibited most of the time because they do have the power to inject virus and worms into the system.

Proposed Firewall for a Computer Network

A firewall is very important to a computer network, especially if this network is being used by a huge number of people. There are a number of possible entry points of viruses and other malicious software. With a firewall in place, these attacks will be minimized. A small college with a relatively small computer network can easily implement a simple firewall configuration. A packet filtering router will be appropriate for the use of the college.
This is a rather simple firewall configuration and this will serve the needs of the college while it is yet growing. An application gateway may be established in the future because this is more secure and will certainly be more useful for the students, the teachers and all those that are connected with the college.

As the organization offers more Internet-connected services to its students and to other stakeholders, it will be necessary to put into place an application gateway. This way, the proxy server can take more of the load of the security attacks that will be directed to the computer network of the college.

This choice of the firewall is being made for a number of reasons. For one, the college in which I came from is still small and does not yet need a very elaborate firewall system. The budgetary requirements of a more complicated firewall system are still not in its best interests at the present time. There are a few other investments that the college has to make in terms of its information technology system. After these investments were made, then the right time for a more elaborate firewall system will then arise.


One thought on “Your Security & Network System: Firewall

  1. Readers are advised to consult, which provides a concise overview of packet filtering and associated problems. While packet filtering is a vital and important tool, it is very important to understand the problems and how they can be addressed.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s