A firewall is a computer software that provides protection from hacking attempts from the Internet. It is very important to install a suitable firewall software to protect the computer from spyware and virus infections. A large number of security companies have developed firewall software. Some of these software are free for personal use.

A firewall software is basically a "packet sniffer". Data that gets transferred via the Internet moves in the form of packets. The firewall software intercepts these packets, analyzes its contents and determines if it is harmful to the computer. If the packet contains malicious content, the firewall blocks it from accessing code on the computer, thus preventing damage to the computer.

Most spyware, malware and virus programs can be prevented by installing a suitable firewall. Firewalls can also prevent software from accessing the Internet and transmitting information without the user's knowledge. Thus even if a virus program gets installed on the computer, it still won't be able to access the Internet and transmit sensitive information like credit card numbers, etc.

The latest version of Microsoft Windows i.e. Windows Vista has an inbuilt firewall in it. This means if you are using Vista, you don't have to download and install additional firewall software. However, if you still want to install a third party firewall, you can do that for added protection.

For maximum protection, it is advisable to invest in an "Internet Security Suite". This is a software bundle that combines a virus scanner, email scanner, spyware protection and a firewall. By installing such software, you can get complete protection from all sorts of malware programs that spread via the Internet.