The problem is often not hardware or software but 'wetware' as the human element is sometimes called. Or to put it another way - "Nothing is fool proof as fools are too ingenious".
Somewhere I worked in the past had a uninterruptable power supply providing smoothed power for the sensitive electronics being used - and the system would crash many evenings for no apparent reason. It was then found that a cleaner was using one of the smoothed power supply sockets in the machine room for a vacuum cleaner putting noise and spikes into the power not realizing the difference between the black sockets with smoothed power and the white sockets for 'domestic' power.