|Draw up a data policy that all employees have to sign|
This is called the "Appropriate Use" policy where I work and clearly details what is, and isn't acceptible with regard to how employees utilize company resources which both the computers work provides, and the network, are.
The employer owns those resources and that gives them every right to say how they can, and can't be used.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.