While this doesn't have much to do with Back Track I will entertain the thread.
First and foremost just because you are being scanned does not mean you are being hacked as per your title.
There are probably millions of scans going on the internet at any one time. As such trying to figure out who or why it is being done would be a waste of your time.
Smarter things to do would be to update your OS to the latest patch level. Update your router if you can. Lock down/ remove all unneeded services and ports.
Be wary of where and how you surf and of course using industry best practices for passwords.
There are a million other things to do (the least of which would be to unplug from the internet) but this will get you started.