Which of the following is a common use of a packet filter in network security?

A packet filter is a crucial component of network security that functions primarily to control access to certain services based on IP addresses, as well as other criteria such as packet type, port numbers, and protocols. By analyzing data packets entering or leaving a network, the packet filter can allow or deny traffic based on predefined rules. This ability to permit or block traffic from specific IP addresses is essential for protecting network resources, ensuring that only authorized devices or users can communicate with sensitive services.

This approach to security is fundamental in setting up firewalls, where rules are established to permit or deny traffic based on the originating or destination IP addresses. This selective access control prevents unauthorized access and helps mitigate various cyber threats, thereby enhancing the overall security posture of the network.

Other choices, while related to different aspects of network management and security, do not align with the primary function of packet filtering. For example, creating backups of network data pertains to data preservation rather than traffic control; improving network performance is more related to optimizing bandwidth and speed rather than filtering packets; and conducting vulnerability assessments focus on identifying security weaknesses rather than actively controlling network traffic. Thus, controlling access based on IP address is the core and most relevant use of packet filters in the context of network security.