There must be policies that have severe consequences if they are violated - demotion, time off with no pay, termination and/or criminal charges (if possible).
Let's not forget my favourite - hanging by the eyelids and beating them until they blink.
Actually, I'm surprised employees are allowed to connect personal devices to company resources. I can't imagine a benefit to the company that comes from such a policy. At least not one that outweighs the potential for catastrophic data loss/theft, trojan horses, viruses, etc. Perhaps I'm just too old-fashioned.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.