Nintendo has confirmed that around around 160,000 Nintendo Accounts have been hacked due to a security breach relating to Nintendo Network IDs.
A Japanese press release, translated by game historian, producer, and localizer Robert Sephazon, explains that a number of login IDs and passwords have been obtained illegally by people outside of Nintendo.
Essentially it looks like hackers have been using older Nintendo Network ID information, which was used to access a range of network services on the Wii U and 3DS, to gain access to associated Nintendo Accounts that are currently used to access Switch services and smart devices titles like Super Mario Run.
As a result of the breach, Nintendo believes hackers will have been able to illegally use credit cards and PayPal accounts, while also accessing personal information such as full names, birth dates, and email addresses.
In a bid to combat the issue, Nintendo is discontinuing the ability to use a Nintendo Network ID to sign in to a Nintendo Account, and is once again "strongly encouraging" users to enable two-step verification for their Nintendo Account.
It will also be resetting the passwords for all Nintendo Network IDs and those Nintendo Accounts that many have been accessed illegally.
"Users will be notified by email to reset your Nintendo Network ID and Nintendo Account. Please avoid reusing the password that you have already used on other websites and services," wrote Nintendo.
"If you use the same password for your Nintendo Network ID and Nintendo Account, your account balance, registered credit card and/or PayPal may have been illegal used on My Nintendo Store or the Nintendo eShop. Please set different passwords for your Nintendo Network ID and Nintendo Account.
"Furthermore, if your purchase history contains unauthorized purchases, than please request to cancel the purchase. We will respond to such requests."
The news was corroborated on the Nintendo Europe support page, which repeated the above advice and said it was continuing to investigate the problem.