Radio Numbers Stations are clandestine radio stations operating over shortwave radio by government agencies. The mysteriousness is due to the cryptic and unintelligible messages transmitted, a stream of numbers, and the lack of information around the intended destination. Sometimes a man or woman may speak the numbers, sometimes the speech is synthesized, and sometimes there’s data but always the destination and message is unknown. With the advent of the Internet these stations may seem a throwback to a more primitive era; however, there are distinct benefits to this old technology. First, shortwave signals carry a great distance.
This makes the transmitters difficult to locate without use of radio signal direction finding(DF) gear. A more important point is that the intended recipient of the message is untraceable since it can be anyone within the radius of the transmission – usually thousands of square miles/kilometers. Anonymity in the age of the Internet is next to impossible so numbers stations protecting identities of intelligence agents in the field is important. And last, the messages are encrypted or rendered otherwise unintelligible. To listen to some real numbers stations check out the priyom.org web site. Also check out The Numbers Station Movie Trailer. I doubt numbers stations are so action packed in real-life but the movie is entertaining.