I'm sure you know that a "firewall" is the metal barrier separating you from the engine of your car. You may have heard the term used in relation to computers as well.

Actually, a computer firewall serves a similar purpose to the one inside cars. Think of a firewall as a gate. It blocks dangerous or untrustworthy information packets from getting into your network.

You should always, always have a good firewall running. Without it, hackers can infiltrate your system, spy on you, upload viruses or steal your data. Usually this takes a matter of minutes.

Windows comes with a decent firewall installed, but many people like using a third-party solution. ZoneAlarm is a free, downloadable firewall and anti-virus that is highly configurable and effective against many kinds of cyberattacks.

There are three versions of ZoneAlarm. The basic one is free and comes with the full anti-virus and firewall combination. If you choose to pay to upgrade to a premium version, you'll get 24/7 customer support, parental controls and PC tuneup services.

Before you download ZoneAlarm, you need to know that you can only have one firewall and one anti-virus running at a time. You can't use Windows Firewall and ZoneAlarm simultaneously, for example.