Firewalls are used to protect a communication network against

A firewall guards a network by blocking unauthorized access and intrusion attempts from outside.

Blocking every virus is the job of antivirus software, which a firewall alone cannot guarantee.

Data-driven attacks hide in permitted traffic and can slip past a basic firewall.

Fire attacks are a physical hazard and have nothing to do with a network firewall.

A firewall filters incoming and outgoing traffic against a set of security rules.

It sits at the boundary between a trusted internal network and the open internet.