Which class of firewall only allows or blocks data packets based on predefined rules?

The choice of a firewall class that only allows or blocks data packets based on predefined rules directly pertains to the functionality of a Packet Filter. Packet filtering firewalls operate at the network layer and function by examining the headers of packets to determine whether to allow or disallow traffic based on criteria established in predefined rules. These criteria might include parameters such as source and destination IP addresses, port numbers, and protocols in use.

Because Packet Filters focus solely on the examination of packet attributes against predefined rules, they do not maintain any context about the state of the connection or inspect the contents of the packets beyond their header information. This simplicity allows for fast performance; however, it may not provide the depth of security found in more advanced firewall types, which can make decisions based on the state of the connection or the data being transmitted.

In contrast, Stateful Inspection firewalls track active connections and make decisions based on the state of those connections, while Application Proxies are more involved as they operate at the application layer and analyze traffic between clients and servers individually. Deep Packet Inspection goes beyond just header analysis by examining the actual payload of the packets to identify and mitigate various types of threats. Thus, the effectiveness and operational context of a Packet Filter is distinctively defined by its reliance