You move it to a high interest bank account and don’t spend a penny. Wait until the bank contacts you asking for it back, you can then ask for proof documenting the error and that they require it back. This often takes quite a while. Once they’ve done it, return their money but you can keep the interest that was made on it.

It won’t be a lot of money, but every little helps.

Honestly you report that shit to the bank if you know what’s good for you, unless $100k is pocket change for you. If you go spending it, they will either get it back from you or you will go to jail for a number of years. Just about any court in the world will consider it the same as if you stole the money from the bank.

Just search and you’ll find numerous cases where that’s happened:
https://www.google.com/search?q=man+gets+million+in+bank+error