The widespread use of broadband services with ADSL connections has significantly improved connection speed and allowed Internet to reach every corner of the globe. However, it has also contributed to increasing the risk of intruders obtaining confidential information or illegally using the resources of computers. Therefore, it is essential to protect IT networks against the growing number of threats.
One of the security tools currently available is the firewall. A firewall operates in network layer 3 to application layer 7 in the OSI model. The main functions of a firewall are the following:
- It filters unauthorized access to computers, through packet filtering or by inspecting the content of the Transport, Session, Presentation, and Application protocol units.
- It warns in case of attack or strange behavior of the communication systems.
- It keeps count of network transactions.
A firewall offers a point where security can be monitored and if suspicious activity is detected, it generates an alert to warn the user of a possible attack or data transit problem.
Advantages of a firewall
- It protects against intruders. It only allows authorized users to access the network, according to the security policies defined.
- It optimizes access. It identifies internal network components and allows more direct communication between these components, if necessary.
- It protects confidential information. It allows access to information based on certain levels of trustworthiness.
- It prevents DoS attacks, as much as possible.
- It controls access to the computer.
- It detects possible fraudulent use.
- It monitors the traffic in the computer.
- It controls access to privileged services.
However, simply installing a firewall does not provide protection on all levels. Below are some of the functions a firewall cannot carry out:
- It does not prevent viruses, worms or Trojans from entering.
- It does not detect intruders. This is a function of IDS.
- It does not monitor network traffic.