Firewalls are used to protect a computer on a network against:

A firewall protects a networked computer against unauthorized attacks by filtering incoming and outgoing traffic.

It checks each data packet against rules and blocks connections that are not allowed.

Fire attacks are literal flames and have nothing to do with a network security tool.

Authorized attacks is a contradiction, since a firewall exists to permit authorized traffic, not stop it.

Internal attacks from within a trusted network can slip past a boundary firewall, so this is not its main aim.

Firewalls can be software on a single machine or dedicated hardware guarding a whole network.