Firewalls

What is a firewall?

A firewall protects your computer from attacks by unauthorised users, either internally (from an organisation’s own users) or externally via the internet. It is also used to stop your staff accessing certain websites. The firewall is able to do this by inspecting packets (*1) of information as they leave or enter the network and then either lets the data through or stops it.

As a result, a firewall can filter information, i.e. information that is sent and received.

The word firewall comes from a comparison originally likened to prevent fires in a building or a ship by using metal walls that could not be burned down. As the fire reaches the firewall it would prevent further damage.

The future of firewalls

All PCs and networks need a firewall simply because as the internet continues to grow and more users gain access, more malicious people will try to gain illegal access to networks, sometimes just for the sake of it, or to steal confidential data or damage users PCs.

Firewalls have to continue to evolve to counter new threats as they develop and as a result, firewalls are here to stay.

Why install a firewall

Leaving your PC or network exposed to the internet without any protection is similar to leaving your car unlocked.

The chances are you may have some valuable items in there and potentially some confidential documents which have been left in a briefcase. As a result, anybody can open the car door and access the interior and its contents. Sure, you could take the risk, but the law of averages dictates that at some point there will either be a break-in or theft of something you value.

This is similar with a PC or a network. Without a firewall it is relatively easy for an unauthorised person to access and steal valuable information, or potentially vandalise and damage your PC.

Types of firewalls

Software firewalls

Advantages:

•    Inexpensive.
•    Easy to configure.

Disadvantages:

•    Needs a computer to run the program and can therefore slow your PC.
•    Requires a copy for each PC on the network.

Hardware firewalls

Advantages:

•    More reliable and less vulnerable to attack.
•    Much better performance.
•    Works on its own computer platform (dedicated computer).

Disadvantages:

•    Hardware firewalls are more complex than software and as such are very difficult to configure to an organisation’s requirements.
•    More expensive because they require their own dedicated computer.

Benefits of a firewall

•    Secures a computer network from hostile intrusions.
 
•    Firewalls can monitor and record information. This can be of value in determining who is accessing what type of information.

•    Firewalls can be used to complement or supplement content and email filtering solutions.

•    Firewalls can automatically block most email viruses and malware (*2) attacks even before they start.

•    Firewalls can be set up to allow access for certain users to access certain information but prevent others from doing so.

•    Firewalls can also calculate usage of the internet, i.e. who spends most time using the internet and how this affects the performance of the network.

•    Some firewalls can cause constraints or bottlenecks on the network as they concentrate security in one area.

•    Organisations need to have a written policy or procedure that outlines what information can be accessed by employees and by whom. A firewall can be used to enforce these policies.

Potential pitfalls

•    Because firewalls inspect every piece of information transferred between users sending information or people downloading information from the Internet, they can slow down the network.

•    You have to bear in mind that running and managing a firewall can be costly in terms of resources and budget. There tend to be issues about who manages the firewall and who decides on the policies, i.e. who can access what information and what websites are appropriate or relevant to the organisational needs.

•    Firewalls cannot alert an administrator that pornographic material is being accessed so it is sometimes best to implement a content monitoring or filtering program as well.

•    Some firewalls claim to be proficient at protecting networks from virus attacks and other malware. This is generally not the case and the user needs to check how effective the firewall is or purchase third party antivirus software.

•    Firewalls can be restrictive in certain circumstances. If, for example, an email with an important attachment such as a business proposal is stopped by the firewall because it is deemed to be in breach of the company’s security policies, it might have an effect on the business.

•    If a firewall is installed incorrectly it can prevent users accessing important information on the internet.

Conclusion

A firewall is an essential element of a security policy for any organisation, small or large.

What type of firewall to run, or whether to choose a hardware or software option, will depend on the size of your organisation and if it has many remote users. For small organisations with maybe less than 10 PCs may find it more practical to have a software firewall on every PC but any more than this will probably necessitate a hardware firewall.

The key to a successful implementation of a firewall is to ensure that it is correctly installed, regularly updated and that you set proper policies to meet the needs of your organisation and users.

Glossary

* – Packets. When information, for example an email, is sent via the internet, the email is broken down into pieces of information or ‘packets’ of information. The packets include vital information including who has sent the information and its’ destination. This ensures that the information is sent to the correct destination.

*2 - Malware. There are many types of computer viruses including worms, phishing, rootkits, and Trojan horses. They are collectively known as malware.