These Secret Cold War Radio Stations Are Still Broadcasting
J Thoendell stashed this in Tech
The leading theory behind their use—albeit one just as speculative as any other—is that these stations are transmitting encoded messages to covert intelligence agents working in hostile territories. It's not like you can just dial up a "cultural attache" working Pyongyang and ask how the spy works is going.
The number station system is, when used correctly, is virtually impossible to detect and essentially foolproof. All the agent requires is a commercially-available shortwave radio and aone-time pad to decipher the message. So long as they're not under electronic surveillance or have the one-time pad discovered, there's effectively zero chance of having the message intercepted and decrypted.