To block user access to MSN messenger, which chain should the firewall rule be placed in?

To effectively block user access to MSN Messenger, the firewall rule should be placed in the Forward chain. This is because the Forward chain is responsible for traffic that is passing through the router and does not originate from the router itself. When users connect to MSN Messenger, their traffic is passing through the router from their devices to the internet. By placing the rule in the Forward chain, you can specifically target this traffic to prevent it from reaching the MSN servers.

In contrast, the Input chain is used for traffic that is destined for the router itself, and the Output chain is for traffic that originates from the router. Since the goal is to block traffic related to a user's request to MSN Messenger rather than to the router itself or originating from it, the Forward chain is the correct choice. The Process option does not exist as a standard chain in MikroTik's firewall configuration, which clarifies that it cannot be the correct answer.