Unit 9 Firewalls

Warm Up

1. What is the purpose of a firewall?

2. What were the first firewalls?

3. Which types of firewalls do you know?

Reading

1. Read the text below and fill in the gaps in the following sentences.

1) Large amounts of information have become available to the average user due to ……………..

2) Firewalls can protect ………………………. from hostile intrusion from the Internet if they are used correctly.

3) ……………………….. were the first generation of internet security feature.

4) A firewall is at the junction point between a …………………… and a public network.

5) Filtering specific types of network traffic is also known as …………………...

Application of Firewalls

The Internet has made large amounts of information available to the average computer user at home, in business and in education. For many people, having access to this information is no longer just an advantage, it is essential. Yet connecting a private network to the Internet can expose critical or confidential data to malicious attack from anywhere in the world. Users who connect their computers to the Internet must be aware of these dangers, their implications and how to protect their data and their critical systems. Firewalls can protect both individual computers and corporate networks from hostile intrusion from the Internet, but must be understood to be used correctly. Firewalls are a very basic part of network security.

The first paper published on firewall technology was in 1988, when engineers from Digital Equipment Corporation (DEC) developed filter systems known as packet filter firewalls. This fairly basic system was the first generation of what became a highly involved and technical internet security feature.

A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. A firewall sits at the junction point or gateway between the two networks, usually a private network and a public network such as the Internet. The earliest firewalls were simply routers.

A firewall examines all traffic routed between the two networks to see if it meets certain criteria. If it does, it is routed between the networks, otherwise it is stopped. A firewall filters both inbound and outbound traffic. It can also manage public access to private networked resources such as host applications. It can be used to log all attempts to enter the private network and trigger alarms when hostile or unauthorized entry is attempted. Firewalls can filter packets based on their source and destination addresses and port numbers. This is known as address filtering. Firewalls can also filter specific types of network traffic. This is also known as protocol filtering because the decision to forward or reject traffic is dependent upon the protocol used, for example HTTP, FTP or TELNET. Firewalls can also filter traffic by packet attribute or state.

A firewall cannot prevent individual users with modems from dialing into or out of the network, bypassing the firewall altogether. Anyone who is responsible for a private network that is connected to a public network needs firewall protection.