Firewalls

Firewalls are used to keep a computer network secure from intruders.

When you connect to the internet via your ISP you become part of a huge network of computers that are constantly communicating with each other through thousands of different entry and exit points called ports. These ports are visible to the outside world when you are online and may be vulnerable to viruses and hackers.

What firewalls do is ‘hide’ your ports from the rest of the internet. They also monitor the ports and, using a set of rules that you customise to suit your own internet use, stop anything unauthorised from passing through.

You can prevent most of the intrusion problems mentioned in this section with the use of software firewalls. Some firewalls are free, while others are relatively inexpensive. A good firewall will be able to detect trojans, stop entry by hackers and prevent unauthorised network access. Unfortunately, firewalls are not entirely effective in preventing port scanning.

A good firewall can also monitor traffic in and out and allow you to install antivirus software, acting as a one-stop shop secure gateway. You can also enable website ‘black lists’ (sites you can’t be visited by users of your network) and make it harder for hackers by setting time limits on traffic or contractors’ access.