It looks like you have PPPoE setup as your internet connection. So the MAC address is the PPPoE server.
You will see a lot _of drops on ports 23, 25, 80, 1433, 3306, 3389, 8080, 8000. They are probes looking for weaknesses.
You can cut down on a lot of them by using a blacklist to filter known attackers.
here is a good start:
http://forum.mikrotik.com/t/blacklist-filter-update-script/89817/1