In the early 1990s,
at the end of the Cold War and before the onset of the Internet Age,
you could tune across the shortwave bands and hear the monotonous
drone of an automated woman’s voice calling out long strings of
numbers in Spanish. “Siete — Quatro — Cinqo — Cinqo —
Cinqo,” the voice would say, pause, and then switch to a new set of
1: A page from the author’s SWL Logbook from 1992 showing the date,
time, frequency and partial transcript of a numbers station
which had started at the end of the Second World War, weren’t
always in Spanish, nor were they always female. Other languages were
used to broadcast entire strings of numbers, which many believed made
up a coded message that could be heard by anyone with a shortwave
radio. The consensus view at the time was they were meant for secret
agents operating in foreign countries.
“We don’t know
for sure what types of agents these messages are being sent to,”
veteran numbers monitor Chris Smolinski told Radio World via
email. ”We also don’t know for sure how the messages are
encoded, although we have some theories.”
include the use of “one-time pad” encryption. The one-time pad
system is almost impossible to crack. It uses a random key or “pad”
to create a cipher text and, once encrypted, the resulting numbers,
letters or bits can be transmitted through virtually any media and
only deciphered by someone with a matching key pad. Destruction of
the key after each use ensures total secrecy.
Today, with the
Internet Age fully mature and the Cold War buried under 20 years of
modern history, the numbers are still being transmitted.
number of stations decreased rapidly after 1990. The British stopped
in 2009 and the Israeli’s in 2011. At least they stopped using
voice transmissions,” Ary Boender writes.
who lives in the Netherlands, has monitored and documented shortwave
numbers stations since 1982. An avid member of the monitoring
community, Boender publishes “Numbers and Oddities,” a monthly
newsletter that lists loggings of shortwave utility stations. He says
the reason the numbers are still broadcast might have a simple
best thing about high frequency (HF) transmissions is that you cannot
trace them and you can hear them with a simple portable radio.”
Since the numbers
are still being transmitted, dedicated radio hobbyists continue to
monitor and report on them.
Chris Smolinski has
been listening to shortwave radio and monitoring numbers stations
since the late 1970s. He maintains www.spynumbers.com
and an e-mail list known as “Spooks,” both of which track and
report loggings of numbers stations. He says he doesn’t know
exactly how many people are listening.
2: A one-time-pad discovered by Detlev Vreisleben after the end of
the Cold War. These pads were used to encrypt and decipher numbers
“I suspect it is
in the low thousands at best, with probably very low hundreds for the
number of dedicated listeners versus those who just occasionally tune
During the spy
numbers heyday there were dozens of stations operating from various
parts of the world. Many were based in Europe, but there were also
stations suspected to be based in Asia, Cuba and even in the United
States of America.
Many of these
stations had developed nicknames within official military or
intelligence organizations and those names often made their way into
the hobby lexicon of the day.
were invented by individual listeners, or the military,” Boender
said. “Bulgarian Betty, for example, was the nickname that was used
by the U.S. military in Germany.”
nicknames for stations derived from pieces of music that played prior
to the actual message or from characteristics of the audio that was
transmitted. These included the “The Lincolnshire Poacher,”
“Swedish Rhapsody” or “The Babbler.”
help sort through the different stations and to bring some level of
coordination to the listening community, a group of European
listeners started naming and classifying each station.
original ENIGMA group invented the classifications,” Boender said.
“The current group ENIGMA 2000 continues this process.”
results were published in the “ENIGMA Control List” which is
still the primary defining document for tracking and reporting these
stations among hobbyists. ENIGMA’s classification system divided
the languages into four rough groups: E for English, G for German, S
for Slavic and V for Various.
Fig. 3: A
communication tower at the Warrenton Training Center facility in
Courtesy of the
Federation of American Scientists
they assigned a sequential number for each unique style of
Spanish-language female voice station became known as “Attenćion,”
due to its repeated use of that phrase at the beginning of each
transmission. Using their classification system, they identified it
officially as station V02.
Boender, who was a
member of ENIGMA, says the listening community has had a big
influence on understanding the origin and intent of these stations.
“Most of what we
know comes from listening, sharing details of the transmission and
schedules, direction finding activities and analyzing all the stuff
that is available,” he said.
V02 “Attenćion” station is believed to be Cuban in origin.
Smolinski says this conclusion is based on careful observation by
hobbyists who occasionally catch stations broadcasting anomalies,
“which the Cuban spy numbers stations are infamous for,”
Smolinski said. “Such as accidentally playing Radio Havana audio
mixed in with the spy numbers transmissions.”
say the phenomenon of numbers stations isn’t limited to foreign
intelligence agencies. ENIGMA designate E05, for example, a station
that used to broadcast a female voice reciting groups of numbers in
English, was last heard in 2003 and was believed to be a CIA funded
and operated station.
“Cynthia,” this station, hobbyists suspect, operated out of the
Warrenton Training Center in Virgina.
While the hobbyists
who monitor these transmissions have always suspected that they were
listening to coded spy messages, to date, no government has
officially acknowledged their existence — something Boender and
Smolinsky would both like to see.
Fig. 5: Google Earth
view of the supposed antennas for V02a/HM01, the Cuban numbers
station that is still active.
Courtesy Ary Boender
would be nice. The fact is that several Russian and Cuban spies were
caught red-handed while listening to the numbers transmissions,”
Boender said, referring to the cases of Ana Belan Montes and Andreas
and Heidrun Anschlag.
Montes, a Cuban spy
who worked for the U.S. Defense Intelligence Agency, was convicted of
espionage in 2002. She had been passing secrets to Cuba for more than
20 years when she was caught. When agents searched her apartment,
they found a small shortwave radio and a piece of paper containing a
matrix of numbers and letters that they believe was used as a
The Anschlag case is
more recent. In 2011 Andreas and Heidrun Anschlag, who had been
living in West Germany for more than 20 years under assumed
identities, were arrested. According to media reports, when a Special
Forces commando stormed the Anschlag’s house he caught Heidrun in
the act of receiving a coded message on a shortwave radio.
NASB NOT CONCERNED
Association of Shortwave Broadcasters is not concerned about the
ongoing use of the shortwave radio spectrum for these transmissions.
Jeff White is the secretary-treasurer for NASB and general manager of
Radio Miami International, WRMI.
“The NASB doesn’t
have an official position on these transmissions,” White wrote in
an email. ”I’m sure we don’t appreciate unofficial,
unlicensed stations encroaching into the out-of-band shortwave
spectrum, but we have not been adversely affected by the stations so
far. As a practical matter, if these are government-run spy
operations, I sincerely doubt that we as the NASB could do anything
Fig. 6: An East
German cypher machine discovered by Detlev Vreisleben after the end
of the Cold War. These machines are believed to be the voice behind
Boender says there
are still several stations that are very active. Most, he says, are
based in Europe — in Poland, Russia and France — which gives him
some advantage in monitoring. The active stations still use English,
German, Slavic and various other languages including Spanish, but the
formats are changing.
“The Cubans are
also active but switched to Redundant Digital File Transfer (RDFT),”
The Cuban station
still uses a female voice to call out strings of numbers, but the
hour-long broadcasts also include digital data bursts. The change in
format also changes the ENIGMA classification and, in this case, the
station has been re-classified as HM01.
listeners in North America, HM01 is easy to hear and, through patient
monitoring, a comprehensive schedule of times and frequencies has
been determined. The schedule is available in Boender’s “Numbers
and Oddities” newsletter.
Thanks to the
efforts of these hobbyists, more than 20 years after the end of the
Cold War, on just about any day of the week, you can use this
schedule to tune in and hear the monotonous drone of a female voice
calling out long strings of numbers in Spanish.
“Cinqo — Cinqo —
Quatro — Siete — Ocho …”
The author, a
technical and freelance writer with a primary interest in radio, has
written for Monitoring Times Magazine, Wonka Vision Magazine, The
Journal of Commerce, Interlake Spectator, The Winnipeg Free Press and