TOKYO - A 31-year-old Chinese national has been arrested in Tokyo on suspicion of operating an illegal mobile phone base station that forced more than 10,000 smartphones onto a 2G network in less than two hours, allowing phishing messages to be sent to unsuspecting users in busy shopping districts including Ginza, Shinjuku and Shibuya.
The Metropolitan Police Department arrested the suspect, identified as Hai Yu, at the scene in Tokyo's Ginza district on suspicion of violating the Radio Act by operating an unauthorized radio station and transmitting illegal radio signals from equipment installed inside a vehicle.
The arrest took place in a crowded commercial area, where investigators surrounded the suspect's vehicle and ordered bystanders to move away. Officers subsequently seized equipment from inside the car, including black and red cables and rectangular silver devices. One investigator observed that the radio transmitter appeared to have been left switched on.
Police believe Yu had turned the vehicle into a mobile fake base station capable of transmitting powerful radio signals that interfered with normal cellular connections.
Smartphones ordinarily connect to legitimate mobile phone towers using 4G or 5G networks. Investigators believe the equipment operated by Yu exploited the tendency of smartphones to connect to stronger signals, first disrupting their normal connections and then forcing vulnerable devices onto an unauthorized 2G network.
The system is believed to have affected smartphones within a radius of approximately 500 meters of the vehicle. Police said Yu drove through Ginza, Shinjuku and Shibuya, interfering with more than 10,000 smartphones in less than two hours.
Investigators suspect the primary purpose was to distribute phishing messages designed to trick recipients into revealing personal and financial information.
One man who reported experiencing a similar incident said his smartphone suddenly switched to a 2G connection while he was walking along a main street in Ginza, leaving him unable to access the internet.
He subsequently received a message written in Chinese claiming that his application account had encountered an abnormality and would be suspended. The message included a suspicious website address and instructed him to log in to a security center immediately, complete an authentication procedure and restore access to his account.
"It was extremely frightening," the man said. "I started imagining that my personal information might be stolen."
Police believe the fraudulent messages were intended to direct users to fake websites where they would be persuaded to enter credit card numbers and other sensitive personal information.
The Metropolitan Police Department has been receiving complaints about similar incidents for approximately two years. According to investigators, 18 people, including Chinese tourists, have reported receiving suspicious text messages while shopping and subsequently discovering unauthorized charges after registering their credit card information.
The reported financial losses total approximately 4 million yen, although police believe the known cases represent only a small fraction of the actual damage.
Investigators are examining whether the fake base station was connected to these earlier phishing incidents and whether similar equipment has been used elsewhere in Tokyo.
Yu denied wrongdoing when confronted by investigators, saying, "I have not done anything illegal."
During subsequent questioning, he continued to deny the allegations, stating, "I did not put any radio equipment in the vehicle, and I know nothing about it."
Police suspect the operation was part of an organized criminal scheme rather than an isolated offense and are continuing their investigation to establish the full extent of the activity, identify others who may have been involved and determine the scale of the resulting financial losses.
Source: TBS
