Do the security p&p thing. One other thing that I haven't hear yet is that you could do is introduce "identifying easter eggs" into the data if you can. Sorry,

Do the security p&p thing. One other thing that I haven't hear yet is that you could do is introduce "identifying easter eggs" into the data if you can. Sorry, not sure what the right word is, but it's a proven technique in certain high level negotiations. You make it easy for this employee to obtain an ever so slightly modified recent version of the data. The modifications are minimal, but allow to identify him as the source of the leak. Document the easter eggs in a registered letter to yourself. Wait until fairly sure the "custom" version of the data is on employee's machine. Then sue if he leaks.