On February 28, Israel and the United States attacked Iran. A few hours later, Iran shut down the internet nationwide, a situation that persists to this day. But something unusual also happened that day: a numbers station began broadcasting a series of numbers. The transmission begins with a warning in Farsi, the language spoken in Iran: “Attention!” and then “two, six, nine, zero, four…”. It repeats several times a day at fixed times and can be heard thousands of kilometers away. The origin of this broadcast first appeared to be Central Europe, although other reports mention southern Europe and the Middle East, and the destination could be somewhere within Iran where agents or operatives have a special codebook to convert those numbers into text. But no one is confirming anything, and there have been no public statements about who is or isn’t the sender of this message, which was first reported by the Financial Times. These broadcasts are known as V32 by the numbers station community.
⚠️ Update: #Iran’s internet blackout is now entering its 18th day after 408 hours without international connectivity for the general public. Chosen users are granted privileged access, while the remainder are left with a limited domestic intranet under increasingly tight control.
— NetBlocks (@netblocks.org) 17 March 2026 at 08:37
Numbers stations had their heyday during the Cold War, but they’ve never really disappeared. In the internet age, they have two major advantages: they work when everything else goes down, and they’re untraceable unless you’re caught red-handed with the codebook. “During the Cold War, they were mainly used to send encrypted instructions to agents abroad or in hostile environments,” says David Marugán, a consultant specializing in security and radio communications. “That essential use hasn’t changed. Today there are fewer visible stations than at the height of the Cold War, but dozens still exist and they still make sense because the digital world is much more monitored, tracked, and controlled. It’s not a resurrected method: it was never abandoned,” he adds.
The conflict in Iran and the potential U.S. attack on Cuba have brought this method back into the spotlight. Its objective is to maintain communication with individuals within a country without them being traceable: “One explanation is that it is a security plan prepared in advance and that has now been activated because other means of communication are no longer available,” says Tony Ingesson, a professor specializing in intelligence at Lund University (Sweden).
The technical elimination of these messages is also very complex. “It’s difficult to completely neutralize it,” says Marugán. A transmitter that generates noise or deliberate interference (jammer) on the same frequency can be used to hinder message reception. “That can significantly degrade reception in the target area, but it doesn’t necessarily eliminate the transmission entirely, nor does it prevent the operator from changing frequencies or adopting other countermeasures, such as adjusting the timing, power, modulation, or even the location,” Marugán adds. The truly effective way to eliminate a station is to physically locate the transmitter and legally dismantle it, which depends on finding it and obtaining the cooperation of the country’s government—something extremely difficult.
“In the case of V32, everything points to the use of the well-known Iranian bubble jammer, a type of jammer that has been associated for years with the censorship of broadcasts aimed at Persian-speaking audiences, such as Radio Farda, Voice of America in Persian, BBC Persia, or Iran International,” explains Marugán.
Another risk is the possibility of the recipients being caught with the codebook in hand, which is also not easy. “The recipient usually writes the message down on paper and then uses a key, also on paper, to decipher it. Once they have transcribed it, they burn both the message and the key. Everything is done with pen and paper, so, unlike any digital device, no trace is left behind,” says Ingesson.
Despite these advantages in critical moments, they are not a useful method for fluid communication with an operative. It is only one-way, which is both an advantage and a disadvantage. It is more difficult to detect potential spies in a given area: “Anyone can hear the signal, but the receiver doesn’t transmit anything back, so it leaves no traffic, it’s completely passive, and it’s technically impossible to locate those who receive it,” says Marugán. But this means that those same agents need other channels to respond, if necessary. “There has to be another channel for the agent or the source to respond: face-to-face meetings, dead ends where messages can be left, another radio transmitter on a different frequency,” explains Ingesson.
Although the attack on Iran may have revived interest in this tool, that is not the country where these stations have been primarily used, Marugán points out: “Cuba is the country with the longest tradition of numbers stations.” The Russian agents arrested in the U.S. in 2010 were listening to numbers stations broadcasting from Cuba. Here you can hear a recent example from the Cuban station HM01, one of the most well-known in the intelligence world.
The Russian-Cuban connection is behind one of the largest uses of numbers stations in history, according to Ingesson: “Number stations are usually associated with very few operators these days, mainly Russia and Cuba. But there is also a Polish station, and Ukraine had one until the large-scale invasion of 2022.” “There is also such a transmitter in Taiwan,” he notes.
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