You can add this to block ping from user who tries more than just ping.
If anyone for some reason try to reach any port on my router(s) that are not open, they are blocked to access any thing on my router (ICMP/web ++) for 24 hours. If they are testing out my router, they have nothing here to do.
More info here: http://forum.mikrotik.com/t/configuration-to-block-users-that-tries-to-access-router-on-non-open-port-s/151840/1