Which of the following is NOT a possible action of the ip firewall filter?

The action that is NOT a possible option for the IP firewall filter in MikroTik is blocking, which is commonly misunderstood. In MikroTik terminology, "block" is not defined as a standalone action for the firewall filter. Instead, the primary mechanism for discarding unwanted packets is through the "drop" action, which effectively terminates the processing of those packets at the firewall level.

On the other hand, actions such as "tarpit," "add-to-address-list," and "log" are specifically designed functionalities within the MikroTik firewall framework. Using "tarpit" can slow down the connection for unwanted traffic by keeping the connection open without allowing it to complete, which can deter certain types of attacks. The "add-to-address-list" action allows you to classify traffic by adding the source or destination IP to a specific list for later use in rules, which can be useful for managing repeated or unwanted traffic from certain IP addresses. "Log" is another essential action that is used to record specific traffic for monitoring and analysis, which can help network administrators spot issues or malicious activities.

Thus, while blocking packets is a necessary task within a firewall, it is addressed through actions like "drop" rather than any labeled as "block."