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you need to have an employee that you trust set it up in a new datacenter. If the employee is not trustworthy, he can repurpose the miner to mine on a pool account that does not belong to the owner of the miner.
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While what you suggest may well happen or may even be common, it's not hard at all to completely lock down the miner sub-network in a data centre, to avoid this, and to increase network performance at the same time ...