If you’re a spymaster, which technology do you choose for communicating with your agents in the field? Calls to an unregistered mobile phone? Encrypted emails? Hidden web pages? Maybe all of these methods are in use – there’s really no one to ask – but there’s one method that is definitely used and, if you feel so inclined, you can check it out for yourself.
The method in question is the numbers station. These are just like ordinary radio stations except that, instead of broadcasting programmes to entertain, they broadcast strings of numbers, read out either by a person or by a computerised voice synthesiser. Of course, no one will actually confirm that these are messages for agents in the field, but the transmissions have been going on since at least the 1980s, so someone must be finding them useful!
But why use numbers stations – which are undoubtedly expensive to run and maintain – when there are now so many potentially cheaper alternatives? The answer is traceability – or rather untraceability. Emails can be traced, web access can be traced and mobile phone calls can be traced. But it’s totally impossible to trace listeners to an off-air radio broadcast, unless you catch them in the act.
Better still, no special equipment is needed to listen to the numbers stations – almost any shortwave receiver will do. While these are not quite as common as they once were, they’re still readily and inexpensively available from your favourite on-line retailer or auction site. In fact, if you live in a big city, you’ll probably be able to find a specialist store when you can buy one off the shelf in total anonymity! Note that no computer, with its potentially incriminating hard drive is needed.
What do the messages actually mean? That’s their other big advantage for the spymaster: they’re totally uncrackable. They typically consist of groups of five numbers, with each group (probably!) having a specific meaning. For example, 53788 might mean “Meet at the usual place, 7:30 pm tomorrow”. The recipient has a pad where they can look up the code group and check its meaning.
But here’s the twist: it’s a one-time pad. Each page in the pad is used only once for one specific message. Another page is used for the next message and 53788 will mean something totally different – or nothing at all. This makes it impossible for anyone without a pad to work out the content of the messages. The only weakness is that the recipient of the messages must have the pads in their possession, but they’re paper and easily destroyed if there’s a threat of discovery.
The numbers stations use old technology, but they still offer benefits that are hard to beat. If you’d like to hear one in operation and you have access to a shortwave receiver, it’s easy. The stations don’t operate continuously, but they do follow fairly regular schedules, and you can easily find the latest schedules by doing an on-line search for “numbers stations”. It’s not the station operators who make this information available, by the way, it’s a group of enthusiasts who track these stations as a hobby – at least that’s what they claim!
Once you’ve found a convenient time and frequency, just tune in and listen. The stations appear to use a lot of power so in many cases, they’re easy to hear. It’s not the most riveting radio programming you’ll ever come across, but it is quite fascinating to speculate about what’s being said and to whom!
Check out some previous stories from Keith on his time as an apprentice...