Nintendo said over 160,000 accounts have been hacked, due to attackers abusing a legacy login system. Nintendo said attackers have been abusing the NNID (Nintendo Network ID) system since the beginning of April to hack into the accounts. The Japanese consumer electronics giant said it is also resetting passwords for affected accounts. It advised players to set up two-factor authentication to add another layer of security to their accounts. Nintendo did not provide further detail about how attackers had accessed the accounts other than to say they were obtained illegally by some means other than our service.
Source: https://threatpost.com/nintendo-confirms-breach-of-160000-accounts/155110/