What action does the firewall take for packets that are matched but not explicitly allowed by a rule?

When a packet matches a rule in the firewall but is not explicitly allowed, the firewall typically takes the action to drop the packet while also logging the event. This behavior is designed to enhance security by ensuring that only recognized and permitted traffic can pass through the firewall. By logging this dropped traffic, administrators are provided with valuable insights into potential security threats or misconfigurations that may need to be addressed.

Logging the event serves as a critical function because it notifies the network administrators about suspicious activities or unauthorized access attempts that could compromise the security posture of the network. This allows for proactive monitoring and response to potential security issues in real-time.

The other options do not align with standard firewall behaviors. Silently dropping packets would mean there is no log for the event, making it difficult for administrators to be aware of potentially malicious activity. Allowing the packets through contradicts the principle of restrictive security, where only explicitly permitted traffic is allowed. Returning packets to the sender is not a common firewall behavior, as it could reveal information about the network's structure and potentially open avenues for attacks.