Japanese social media is buzzing with speculation about fake base stations believed to be impersonating NTT DOCOMO, the largest mobile operator in Japan, and scams run by Chinese gangsters. The story was instigated on Saturday by a user named ‘Radio Yakuza’ (電波やくざ) who posted about the discovery of a transmitter interfering with mobile phone connections on his @denpa893 account with X, formerly known as Twitter. There have been millions of views for Radio Yakuza’s posts since then. Public concern about potential SMS blaster smishing crime in Tokyo and Osaka prompted questions for Seiichiro Murakami, the Minister of Internal Affairs and Communications, at a press conference held on Tuesday. Murakami refused to talk about the specific evidence presented by Radio Yakuza but said he was aware of cases of radio interference with mobile networks. The following is taken from the official transcript of Murakami’s press briefing, with a translation below.
偽基地局による違法な電波発信
問：
SNSで都内や大阪市内の都市部で偽の基地局を装って発出されたとみられる違法な電波が検出されて、フィッシングメールなどが送られているような実態が話題になっているのですが、そのことについて、総務省として現状把握がどのようになっているのかということと、今後の対応などをお聞かせください。
答：
都市部で偽基地局による違法な電波発信が確認されたと、SNSで話題になっていることは聞いております。
事柄の性質上、個々のSNSの投稿の内容の真偽も含め、個別具体的な内容については、回答を差し控えさせていただきたいと思います。
他方、都内周辺等で携帯電話サービスへの混信事案が発生していることは把握しております。現在、関係機関と連携して対応にあたっております。
総務省では、引き続き、誰もが安心して電波を利用できる環境の確保にしっかりと取り組んでまいりたいと考えております。
Illegal radio wave transmission from fake base stations
Question:
There has been a lot of talk on SNS [Social Networking Services i.e. social media] about illegal radio waves that appear to be emitted from fake base stations in urban areas of Tokyo and Osaka, and phishing messages and the like being sent. I would like to know how the Ministry of Internal Affairs and Communications is interpreting the current situation and what future measures it plans to take.
Answer:
We have heard that there has been a lot of activity on social media about illegal radio wave transmissions from fake base stations in urban areas.
Due to the nature of the matter, we would like to refrain from commenting on specific details, including the veracity of individual SNS posts.
However, we are aware of cases of interference with mobile phone services occurring in and around Tokyo. We are currently working with relevant agencies to address the issue.
The Ministry of Internal Affairs and Communications will continue to work hard to ensure an environment in which everyone can use radio waves with peace of mind.
That is an extraordinary admission by the standards of Japanese culture. Social order is a high priority to the Japanese. The reaction to Radio Yakuza’s post on social media is confirmation of how many Japanese are shocked by the notion that their phones may be connecting to illegal radio devices that impersonate their phone company. Murakami chose not to dismiss the claim that they are being used as SMS blasters to send smishing messages. This is telling. Authorities in other East Asian countries openly warn the public about the danger of smishing messages sent by SMS blasters. It is likely that Murakami is trying to avoid panic whilst simultaneously wanting the public to become more sensitive to the risk of fraud as a consequence of this news being informally spread via social media.
The amount of social media engagement for this story is not being exaggerated. Google identified ‘mobile base station’ as one of the top trending search terms in Japan on Monday. I did not learn of this story through my normal methods; it was obvious something unusual was happening because Commsrisk has received a surge of traffic from Japan during the last few days. This traffic concentrated on Commsrisk’s articles about SMS blasters. The follow-on examination of social media activity indicates many Japanese are comparing what has been reported by Radio Yakuza with stories about the way SMS blasters have been used for smishing in other countries.
Visitors to Commsrisk from Japan have been especially keen to examine photographs of equipment seized by police in other countries. They identified startling similarities with a device that Radio Yakuza photographed in the back of a vehicle in Tokyo. Some initially noticed that a bright orange object captured in Radio Yakuza’s photograph appears to be a DC-to-AC power inverter that looks similar to one highlighted in a Commsrisk story about a Hong Kong police SMS blaster seizure during late February. Another eagle-eyed social media user then observed it is also similar to a device from a Commsrisk story about an SMS blaster raid by Malaysian police in November 2024. And then yet another power device with the same distinctive case was noticed in the corner of a photograph from a Thai SMS blaster raid in January 2025. In each photograph we see a device that has electrical sockets, is in a case that has the same shape and color, and would be needed to power equipment from the vehicle’s battery.
The association with the Hong Kong story, and the fact that the Thai bust was connected to Chinese gangsters then fueled further speculation about Chinese gangs driving SMS blasters around Japan. Keep reading for the evidence that ordinary Japanese people have gathered about crimes with a strong Chinese aspect to them but which the Japanese authorities seem unwilling to talk about.
Radio Yakuza’s excellent detective work was first motivated by his receiving a ‘weird SMS’ as he was walking around. Per his post on X:
なにこれこわーい
街中歩いてたら
もう日本で見れるわけないEピクト(GSM)になって
突然変なSMS送られてきた～
しばらくドコモ圏外だったし
何が起きたんだろーこわいなーWhat’s this, so creepy
Walking around town
And suddenly it switched to E pictogram (GSM), which you shouldn’t see in Japan anymore
Got a weird SMS out of nowhere~
Was out of Docomo service for a while too
What happened, so creepy~
Radio Yakuza examined what was happening with his phone and joked that “being told to fall back to GSM from the base station feels fresh lol”. Regular readers of Commsrisk will immediately see the connection to many reported cases of SMS blasters undermining security safeguards by prompting the phone to switch to a 2G connection. Radio Yakuza then identified the car where the transmission was coming from and took a photograph of it. He observed that the high output of the radio device would necessitate a fan to keep it cool. That post has been viewed 5 million times at the time of writing.
The analysis continued with Radio Yakuza establishing the device in the car was presenting itself as part of the DOCOMO network although his phone was unable to get a connection to a genuine DOCOMO base station. This led him to use a spectrum analyzer to better understand the radio transmissions. Per the screen grabs he shared of his spectrum analysis, it appears he used an NEC SpeCat2 for this work. The results were summarized in the post which instigated the furore by stating “NTT Docomo is being jammed on all bands except Band 3”. Radio Yakuza judged this was due to the “operation of a fake NTT Docomo base station vehicle”. Other social media users then began to offer assistance by suggesting possible criminal motives. This broadening of the search led them to identify relevant news articles about SMS blasters from around the world, including articles on Commsrisk.
Radio Yakuza’s investigation then led to a ‘scary’ new finding: he was also being presented with apparent base stations for Chinese mobile phone networks even though he is in Japan. China Mobile, China Telecom and China Unicom were all listed as networks that Radio Yakuza’s phone could connect with. One possible explanation is that the SMS blaster had previously been configured to commit crime within China and those settings were not overwritten when it was transported to Japan. However, Radio Yakuza then shared the SMS message he received, which appears to be a scam aimed specifically at Chinese tourists. The message presented itself as being from ‘China Unionpay’ and translates as follows.
Due to the risk of overseas credit card swiping, your bank card will be suspended
Overseas payment function, if you need an overseas card, please reactivate [URL redacted]
A URL is then given for victims to click. It has a ‘cn’ prefix suggestive of China, and the top-level domain is .vip, a domain that Chinese high-rollers might associate with their status. Radio Yakuza’s screen grab of the message is copied below.
As Radio Yakuza’s work continued, other people started to recount their stories of ‘radio jamming’. The growing team of amateur detectives became increasingly confident that SMS blasters are being driven around Japan to a greater extent than any of them previously imagined. Radio Yakuza backed this up by searching Chinese social media for stories about fraudulent SMS messages tricking Chinese tourists in Japan. He identified the Ginza and Shibuya regions of Tokyo as the alleged hotspots for this kind of scam activity. Further research of Chinese social media by Radio Yakuza also suggested the same smishing scams had occurred in the city of Osaka, 240 miles (400km) to the West of Tokyo.
The new awareness of the problem prompted a cascade of other phone users to share their news of incidents where they had received smishing messages apparently intended for Chinese tourists, or where their phones were downgraded to 2G connections, or where they were given the opportunity to connect with base stations that presented the names of Chinese networks. This all corroborated the findings from Radio Yakuza’s investigation. If the authorities had been aware of the scale of these criminal activities, they must have consciously chosen not to warn the public about them.
Radio Yakuza and the people who responded to his investigation have done the whole world a favor. They have drawn attention to a crime that authorities typically underestimate because they are not looking for it, and because they have no reliable method of detecting it. However, there is a sting in this tale. The openness with which Radio Yakuza has shared his research, and the generous way other Japanese have assisted his efforts, has not been matched by Japan’s mobile operators. As already noted, Japanese culture values security and stability. This story grew so big on social media that mainstream journalists asked mobile operators what they are doing about fake base stations. Japan’s telcos had to respond, but they gave evasive answers, perhaps because they were scared to be more candid. Per ITmedia News:
携帯キャリア各社も、偽基地局への対策に乗り出している。ITmedia NEWSが問い合わせたところ、NTTドコモからは「妨害電波の被害情報は認識しており、社内外で連携して対応を進めている」との回答があった。
また、ソフトバンクは「疑わしい事象は把握しており、現在関係各所と連携して情報収集・調査を行い、対策に向けた取り組みを進めている」とコメント。KDDIは「状況は承知している。当社への影響は確認できていないが、今後も状況を注視していく」としている。楽天モバイルは「発生については把握しているが、現時点ではサービスへの具体的な影響などは確認されていない。本件については今後も注視していく」とした。
Mobile phone carriers are also starting to take measures against fake base stations. When contacted by ITmedia NEWS, NTT Docomo responded, “We are aware of the information about the damage caused by jamming signals, and we are working together both internally and externally to address the issue.”
SoftBank also commented, “We are aware of the suspicious incidents, and are currently working with relevant parties to gather information, conduct an investigation, and take measures.” KDDI said, “We are aware of the situation. We have not been able to confirm the impact on our company, but we will continue to monitor the situation.” Rakuten Mobile said, “We are aware of the incidents, but at this time we have not confirmed any specific impact on our services. We will continue to monitor this matter.”
These responses are flimflam from companies who do not want to admit they do not know what to do. Partly this is because they were asked the wrong question. Nobody asks Toyota what they do to stop drunken drivers crashing cars because a car manufacturer cannot control how a human being behaves. By the same token, a mobile operator cannot control how gangsters use radio devices that have no connection to their networks. These messages only appear to come from a mobile operator; the operator has no awareness of the message because neither the SMS blaster nor the victim’s phone are connected to a mobile network when the message is sent. Any response to SMS blaster crime depends on police acting urgently on the limited intelligence an operator can provide about the rough area where they notice a temporary disruption to their service. Criminals put SMS blasters in cars. Law enforcement needs to be at least as mobile to counteract them.
Unless Japan’s authorities are going to deputize telcos so they can make arrests, it is the responsibility of law enforcement agencies to send officers to the locations where SMS blasters are believed to be operating, so they can pinpoint them and arrest the people found using them. More importantly, the police will probably only arrest low-level stooges in the criminal enterprise, who may not even be aware of the purpose of the radio transmitters they are driving around. The police need to conduct interrogations and follow-on investigation work to identify the bosses who orchestrate these scams. Otherwise, the scamlords will simply buy new SMS blasters and hire new drivers to replace the ones who were imprisoned. Because the burden on police is considerable, lawmakers should also criminalize the use of SMS blasters and task customs staff with preventing their importation. These are strategies that have been adopted with some success in countries like Thailand and the Philippines. It is no coincidence that countries with the most sophisticated, comprehensive and rounded strategies for tackling SMS blaster scams are also the countries where both the public and the authorities are most open and aware of the scale of the challenge they face.
It may be a while before Japan’s authorities are ready to properly tackle this phenomenon. In the meantime, credit is due to Radio Yakuza and all the people who have helped his investigation. This story, and the way it became public, will encourage more vigorous action against SMS blasters in other countries too. The revelation that an apparently identical bright orange power inverter was found in cars circling Kuala Lumpur, Bangkok, Hong Kong and Tokyo is persuasive evidence of international gangs running scams on the same systematic basis across multiple countries. I applaud Radio Yakuza for his public-spirited actions and encourage everyone who contributed to keep reporting new incidents of suspicious 2G downgrades and scam SMS messages received around Japan. Without public pressure, it is unlikely that people in power would ever learn of the scale of criminality conducted outside of the bounds of conventional networks. Radio Yakuza and everybody involved in sharing these revelations has done a service for phone users in Japan and worldwide.
Look below to compare photographs of the power inverters seized by police in greater Kuala Lumpur during November (top), Bangkok during January (second), Hong Kong during February (third), and the one photographed by Radio Yakuza in Japan this April (bottom).
