> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://help.ex2.com/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# What is a Firewall?

## The digital firewall concept

A firewall is a set of rules governing incoming and outgoing connections to a network or device. The role of firewalls is to protect a system from intrusions and unwanted connections.

Firewalls can take the form of hardware or software applications. The most common type of firewall protects home devices (PCs, smartphones, etc.). They limit what types of outgoing connections can be established and what incoming requests are allowed.

In enterprise systems, firewalls can represent much more complex and precise sets of rules. Some advanced firewalls allow you to monitor packets, identify malicious traffic, or filter data at the application layer level.

There are several types of firewall software that can be used. Most operating systems also integrate their own firewall software.