How German's foreign intelligence service, the BND, protects itself from moles

08 Feb 2019: Chancellor Angela Merkel and Bruno Kahl, the president of the BND, before the opening ceremony on Friday. The building has 14,000 windows and 12,000 doors. Photograph: Florian Gaertner/Photothek via Getty Images

What shouldn't happen happened. A BND employee was probably spying - for Russia. It is still being determined. And the question ari…