Getting kicked offline!!??

Not using their own console they can't. The attack is done with a PC. There is no issue with the security of Xbox Live as the attack doesn't come through Live.

 

Okay, so they used a PC with which to set up and carry out the attack. But where did the attacker 1st make contact with his/her victum?

So XBL security, or lack thereof. Which MAY allow back door access for gaining IP addresses, and/or other perhaps even more personal info is still the main concern here is it not?

 

OP I am just going to go ahead and say that there is likely nothing you can do - within reason.

Examples: If you file suit, your Lawyer, their's and even the criminal injustice system itself will make money and you will likely wind up in debters prison.

As for ISP. They are just as lkely to take your report and file it under F as they are to actually do something about it. This being an election year. You could make a stink, but lawmakers love using tech GIANTS back doors to get around The Constitution,
and Bill of rights.

So whats a body to do?

I would just have my ISP address changed. And along with it, my tag. At least in the short term you could have some piece of mind.

 

It's easy to grab an IP from an online game, anyone can do it. No matter the platform you game on. Not going to post a link to how as that would be asking for a ban but a simple Google search will show you.

Problem is here that there is little that Microsoft can do as the person is not attacking the Live service but the user's internet connection. There's no way for Microsoft to know if you are suffering a DDoS attack or just have a poor connection.