With disposable encryption in mind, number stations have provided the perfect way to send encrypted messages across the planet without arousing suspicion. Although it may seem easier to send instructions through the internet, radio broadcasts have the advantage of reaching everyone and hiding the real intended recipient. However, this doesn’t mean that these stations are totally invisible.
As one Reddit user explains, several of these mystery stations have been identified and linked back to their operating countries through the use of radio signal triangulation. Due to the scrambled nature of the signal itself, a country carries no real risk even if the physical location of its stations is discovered.
“By design a directional antenna receives best in one direction. You mechanically turn the directional antenna until the signal is strongest, this indicates the direction of the source from your location. You then plot a line of bearing on a map from your location along the indicated direction. If you do this from 2 or more locations, or 2 or more stations do it at the same time, the lines of bearing intersect at some point on the map. That point is the approximate location of the source.”
A series of arrests in the US in 2010 has helped shed light on how active these stations still are. The FBI announced that it had broken up a “long term, deep cover” ring of Russian spies across the United States, who had been receiving coded instructions via one of these “ghost” stations.
North Korea has also begun dabbling with these stations. After a 16 year absence, the country’s single source of secretive transmissions started broadcasting again in 2016 and South Korean authorities fear they may be used to coordinate terrorism. Unlike the more advanced stations used in the West, North Korea’s system has made little effort to hide the fact that it’s transmitting encrypted messages.
“On page 459, question number 35, on page 913, question number 55, on page 135, question number 86, on page 257, question number 2…”, reads the announcer of the first broadcast on July 15th, 2016. Although these phrases can be easily read as code, they’ll stay secure as long as the key used to create them remains in the right hands. The creepy white noise that internet amateurs have been cataloging may have been military instructions from a foreign government all along.