He got really excited when we approached a business meeting room, that, after the door opened, looked like any other of hundreds of meeting rooms I’ve seen. “The walls,” he told me while patting the wallpapered surface, “contain shielding. The electrical outlets are specially protected and isolated. The telephones are specially wired to allow encryption devices.”

Shielding started years ago, primarily as a way to protect electronic equipment from electromagnetic interference (EMI) and radio frequency interference (RFI) coming from other equipment and devices nearby.