Hi there Julia C, I am Lumie and I would love to assist you today.
I am so sorry you are having issues with a brute force attack.
Microsoft will not give you their Internet Service Provider information however their IP is directly listed on your activity page on the left. I will warn you, these are usually bot net clients, normal users who have malware forcing them to make requests to your account.
Please keep in mind, with two-step verification, you should not have to be concerned too much about the security of your account.
However it does pose some risk, and can lead to the blocking of your account as you have seen.
Thankfully, I have the perfect solution!
"Go to Add an alias.
Sign in to your Microsoft account, if prompted. [https://account.live.com/AddAssocId]
Under Add an alias, do one of the following:
Create a new Outlook.com email address and add it as an alias.
Add an existing email address as an alias.
Select Add alias."
These steps and more information can be found here: [https://support.microsoft.com/office/459b1989-356d-40fa-a689-8f285b13f1f2]
Now you can go to this site: [account.live.com/SignInPreferences] and turn off your sign in options for the past alias.
Your email address will operate completely as normal, but now you must sign in with another email address.
I hope this helps!
Let me know if I can be of any further assistance. -Lumie =)