What is a firewall?

What is a firewall?

A firewall is a network security system that acts as a filter for data entering or leaving a network or computer preventing unauthorized people access to or from a private network.
All messages entering or leaving the network pass through the firewall, which examines each message and blocks those that do not meet the user specified security criteria.
A firewall establishes a barrier between your company´s network and the Internet, this way you can control whether to allow or block specific traffic based on a set of security rules.