Which of the following best blocks unwanted traffic on a network?

A firewall examines network traffic and permits or blocks it according to configured security rules. Rules can be based on characteristics such as:

Source or destination IP address.

Network protocol.

Source or destination port.

Connection state.

Application or service.

Direction of communication.

This makes a firewall the device that most directly blocks unauthorized or unwanted network traffic.

An access point provides wireless network connectivity.

A switch forwards Ethernet frames between devices on a local network.

A router directs packets between different IP networks. Some routers contain integrated firewall functionality, but routing itself is not the primary security control described by the question.

CompTIA objective 2.5 includes firewalls among common network hardware devices. Microsoft describes a firewall as a technology that filters network traffic and blocks unauthorized access.

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