broadcast

i can block it? if yes how do it?

read this document to know how you can drop broadcasts and how /ip firewall filter works:
http://www.mikrotik.com/testdocs/ros/2.9/ip/filter.php

yes ok but i can block it or no? which i can block?

If you read the doc you will see that you can block the broadcast

M.

can you tell me how i block the broadcast?

OMG…
New firewall rule → Extra → Dst. Address Type → Broadcast