How do you make a tab (or menu) less accessible?

We have a pop-up menu with 3 tabs. All three tabs rank in importance. When clicked on an element in a page, you get a pop-up with the first (base) tab active where you see all the information you actually need. In some cases you want to click on another tab in that pop-up, although that's not that often. In even more extreme cases, you want to access a third tab, which contains very specific and somewhat sensitive information that we would like the users to access only as a last resort. In that sense, how can we make such tab less accessible to the user so he wouldn't enter it without the need for it?