I've seen this at banks that do something similar (and it's probably for this reason). They include a user-selected picture at logon, so if you see the wrong picture, you know that their logon page is being spoofed.

I have no idea of the feasibility of locking down some piece of user data such that the OS can display it for privileged access, but random apps cannot, but this seems like a reasonable solution. Include some user selected word or picture in the title bar of the settings dialog so that users know its the real one.