I am currently getting cyber attacked through my wifi. Sombody can connect to my macbook pro and log in as a user account which is apparent by looking at Terminal. Is there anyway I can change the firewall settings at all?
Your computer wil have 2 MAC addresses (at least) one for teh wired Ethernet and one for the WiFi interface. Have you compare the dubious one against both of them.
The fact that they are able to access your MAC means that something is installed there. I would recommend an OS reload here just to make sure.
Then try to run a packet tracer and see if the traffic is still there.