How the Iran war has seen the return of Cold War spycraft

Description

It sounds like something from a spy novel: a calm voice reading strings of numbers over shortwave radio at the same time every day, with no explanation or signature. Yet in early March, multiple outlets reported the appearance of a mysterious Farsi-language broadcast on shortwave, timed closely after the opening phase of the US–Israeli bombing campaign against Iran. The description matches what is known as a number station, a brutally simple form of communication. A transmitter broadcasts coded content (often spoken numbers, sometimes tones or short phrases) intended for a receiver who already possesses the key to decipher the message. The receiver does not need an internet connection or a phone. They only need to listen at the right time, decode offline, and disappear back into ordinary life. The advantage is easiest to grasp through a lighthouse analogy: the beacon is visible to everyone, but it cannot see who is watching from the dark sea. In the same way, a state can broadcast a signal widely without knowing which specific listener is receiving it. Anyone can hear the signal, but only someone with the key can make sense of it.