Nintendo Network IDs have been hacked, leading Nintendo to disable login via the system.
~Nintendo.We are aware of reports of unauthorized access to some Nintendo Accounts and we are investigating the situation.
As one action in our ongoing investigation, we are discontinuing the ability to use a Nintendo Network ID to sign in to a Nintendo Account. All other options to sign in to a Nintendo Account remain available.
As a further precaution, we will soon contact users about resetting passwords for Nintendo Network IDs and Nintendo Accounts that we have reason to believe were accessed without authorisation.
Users are recommended to enable and use two-factor authentication to secure their accounts.