Nintendo said 300,000 Nintendo Network ID (NNID) accounts were broken into as part of a hacking attempt in April, which is nearly twice as many as initially stated. Nintendo previously said that 160,000 accounts were broken into.
NNIDs were used for the 3DS and Wii U and allowed users of either system to download content and link their systems to a shared wallet. A new account system was used for the Nintendo Switch, but 3DS and Wii U owners could link their accounts.
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https://www.theverge.com/2020/6/9/21285084/nintendo-nnid-switch-hack-accounts-affected-exposed