What is the primary function of a packet filter in a firewall?

The primary function of a packet filter in a firewall is to inspect packets and allow or block them based on security rules. This process involves examining the headers of each packet, which contain important information such as the source and destination IP addresses, port numbers, and the type of protocol being used.

By applying predefined security rules—configured by network administrators—the packet filter can decide whether to allow a packet through or block it. For example, if a packet comes from a trusted source and is requesting access to a permitted service, the packet filter will allow it. Conversely, if a packet is deemed suspicious or comes from an untrusted source, it can be blocked, helping to maintain the integrity and security of the network.

This function is critical in protecting networks from unauthorized access, attacks, and various network threats while allowing legitimate traffic to flow smoothly. Other options, such as encrypting data or blocking all connections, do not represent the primary purpose of packet filtering; rather, they involve separate security functionalities that do not directly pertain to the filtering of packets based on established rules.