Which of the following offers protection against unauthorized access by filtering incoming traffic?

A firewall is a network security device or software that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It serves as a barrier between a trusted internal network and untrusted external networks, such as the internet. By filtering incoming traffic, a firewall helps to prevent unauthorized access to the network, blocking harmful traffic while allowing legitimate communication.

This filtering capability is essential for protecting sensitive data and maintaining the integrity of network resources. In contrast, antivirus software primarily focuses on detecting and removing malware on devices, an Intrusion Detection System (IDS) monitors network traffic for suspicious activity but doesn't actively block it, and a network monitor gathers and analyzes data about network performance rather than providing access control. Therefore, the correct response highlights the specific role of a firewall in ensuring secure network connectivity.