A firewall is one of the most important weapon used to keep computers safe from hackers. A firewall automatically examines every bit of data that comes in or goes out of the computer via the internet. A firewall either allows or denies access to the computer based on a set of predetermined rules.

For most users, a default setting is good enough to deny access to the computer. But the firewall can be tweaked if the user wants to prevent downloading of files from dodgy websites

Most home computers have a software based firewall. Both Windows and Apple operating systems have built-in firewall, and can be tweaked from the control panel settings.