A barrage of malware is constantly trying to access your systems from outside your network. Without a means to prevent this, your machine is operating with an "open door" policy. All manner of sensitive data, be it financial login credentials, passwords, credit card details, becomes free for the taking to any hacker with an iota of skill.

"Not only can hackers walk straight through the door and help themselves to your data, they can install their own back door, to ensure they can come and go as they please in the future," says Simon Campbell-Young, CEO of Phoenix Distribution.

This is why he says it is vital to have a firewall in place. "Firewalls prevent access to your system from outside. Firewalls not only prevent unwanted attacks from outside, but also, where infection of the system has occurred, can prevent the malware program contacting its command and control (C&C) servers, and doing even greater damage such as downloading additional malicious software or exfiltrating sensitive information."

He says there are two basic types of firewalls, either hardware or software-based ones. "The former are physically stationed in the middle of the Internet connection and the network. Other equipment such as DSL routers usually have basic firewall functionality included. These firewalls essentially separate the internal network from the Internet."

The latter, he says, is a piece of software that is installed on a PC in order to protect it from unauthorised access. "Today's operating systems have integrated software firewalls but do not always include the full functionality enjoyed by separate firewall software. Standalone firewall software is installed directly onto a computer, and functions as a sentinel to control and monitor network traffic, and protect the system."

Also called a personal or desktop firewall, Campbell-Young says a specific rule set will help the firewall decide which network packets may enter the network and which should be blocked. The firewall will decide this based on several different criteria. These will include the IP address or port number, and of course the connection itself, or the application in question. New rules can also be created to cover any eventuality not covered but the existing rule set.

"Firewalls are a hugely effective means of blocking Internet threats, which can seriously damage your business. Firewalls ensure that incoming or outgoing information has to pass through it, making the firewall effectively the strategic point for all data exchange. Focusing security efforts on this point can be an enormous time saver."

Firewalls also help the business to enforce its security policies. "There are access protocols that are best kept within your network and others that are best kept out totally. Moreover, it is crucial to be able to allocate certain privileges to specific users within your network and no others. A firewall will help enforce these rules and privileges," Campbell-Young says.

Finally, since the firewall is the information exchange gateway of the business, access to those activity logs give a full view of what is happening on your networks.