Hackers breached around 300,000 Nintendo Network ID (NNID) accounts in April, the Japanese gaming company has revealed.
The NNID account was previously used for the 3DS and Wii U consoles and allowed users to download content and link systems to a single shared wallet.
It was replaced with a new account system with the arrival of the Nintendo Switch, but users were still able to link their NNID and Nintendo accounts.
Following account holders reporting unauthorised purchases made on their accounts, the company confirmed 160,000 accounts had been accessed by unauthorised parties after their login details and passwords had been obtained in an illegal manner.
On Tuesday, however, it announced further investigation revealed an additional 140,000 accounts were compromised.
The company warned people who used the same password for their NNID and Nintendo accounts were at risk of their wallet balance, registered credit card, or PayPal being used for purchases on the My Nintendo Store or Nintendo eShop.
The breaches also exposed personal information such as user nicknames, birthdates, locations, and email addresses.
Login option removed
The company has removed the option to log in to a Nintendo account via NNID and performed password resets on NNID and Nintendo accounts that may have been logged into by malicious parties.
It also advised users to enable two-step verification for additional protection of their accounts.
Nintendo said a very small fraction of compromised accounts were used for fraudulent transactions.
“Less than 1% of all NNIDs around the world that may have been illegally logged in may have actually been fraudulently traded through their Nintendo account,” it stated.
The company said it was still busy refunding affected customers in each country, and added that most refunds had been processed.
Nintendo has seen a substantial surge in sales of its Switch consoles as the COVID-19 pandemic has forced people to entertain themselves at home.
According to figures from NPD Group, sales of the console doubled in March when compared to the same month in 2019.
Nintendo’s Animal Crossing: New Horizons was the best-selling video game in March and was second only to Call of Duty in sales for the entire 2020.