The correct answer is Unauthorized attack.Firewall:A Firewall manages the secure in-flow and out-flow of data in a device.It monitors the network traffic and acts as a barrier between the trusted and untrusted networks. A firewall is used in communication networks/systems for protection from Unauthorized attacks.The concept of a Firewall is important for people interested in understanding the network security aspect of a computer device and also for those looking forward to strengthening their Computer Awareness.A Firewall is a security system to protect an internal network from unauthorized servers and networks based on predefined rules.It acts as a barrier and only allows the secured network to send or receive data.Additional InformationTypes of Firewall:Packet Filtering Firewall:It is one of the oldest types of Firewall.This type of Firewall creates a checkpoint at the traffic router.Only the secure and verified IP address or networks are allowed for the further flow of data.Application Level Gateway Firewall:It is also known as Proxy Firewall.When the user connects with the destination server, it forms a connection with the application gateway.The proxy then connects with the destination server and takes up the decision of forwarding the data packets.Circuit Level Gateway Firewall:This works as the Sessions layer of the OSI Model.Using this, two Transmission Control Protocol (TCP) connections can be set up together.It can easily let the flow of data packets continue without consuming major computer resources.Stateful Inspection Firewall:It is a combination of data packet inspection and TCP connection.Until both the fields are verified, the information cannot be approved.They are less straining for the computer resources.However, they are a bit slow in comparison to other Firewalls.