Have you ever used Citibank ATMs? Did you notice that the ATM screen after dispatching the money, shows up your account balance to everybody standing in the queue. No looking over the shoulders is required here.
The ATM screen is placed in such an angle that it is clearly visible to all the people standing behind in the queue (even though the queue is about 5 to 6 ft away). Either the screen could be mounted at a lower angle such that it is visible to only the user or else the viewing angle of the LCD panel could be reduced.
As a workaround, the only option left is to hide the screen from others!