You need to block that address at nicehash and stop paying them any balance they have.
Thanks for that notice. Now, it's not that easy to simply accuse one Bitcoin address owner to be hacker, because one could easily just pick one Bitcoin address, say he's a hacker and make the pool to block his address (the pros and cons of anonymity). So we have to be careful and double check this kind of situations - nevertheless this seems like a suspicious case, therefore we blocked the payouts of this Bitcoin address.
Best regards,
NiceHash
You will also see at nicehash that his hacking is the equivalent of a botnet and originating from any IP address his hacking is successful.
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Edit: in fact if the miners themselves have used nicehash, you will probably even be able to associate those IP addresses back to anyone who has used you service and been hacked by this hacker and be able to return the BTC to the original owner.
No guessing and no confusion for some of them.