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On Android phones, there's a feature turned on by default that lets them fall back to 2G connections. According to police in Tokyo, a man had been exploiting that feature from a car, and they have now arrested him. On November 7, police closed in on a dark blue hatchback on a Ginza street. Under the back seat was a radio transmitter, still on, with batteries in the trunk. The device, police say, emitted a strong signal on the same frequencies as the carriers, causing every phone within about 500 meters of the car to lose its connection: more than 10,000 phones. When a phone loses its connection, it looks for any network to connect to, and what the car was emitting was a 2G connection. On 4G and 5G networks, a phone checks whether the cell tower it's connecting to is legitimate. On 2G, it doesn't, and so any phone that connected to the car's fake tower had no way of knowing it wasn't legitimate, and trusted everything it saw. What it saw was a text message, in Chinese, saying the recipient's credit card had been suspended and offering a link to fix the problem. Police say 18 people, mostly Chinese tourists, lost around 4 million yen to the scam, or around $25,000. The driver, Yu Hai, a 31-year-old Chinese national, denies the allegations. One man in his 20s told NHK that when he was walking in Shibuya, his phone suddenly switched to 2G, and that exact text message appeared on his phone. He ignored it. Japan doesn't have a 2G network. It shut down its last one around 2012. Why would a phone in Tokyo still connect to one? Because phones are built for the global market, and some parts of the world still only have a 2G connection. That's why the setting is left turned on. If it were turned off for everyone, then a traveler in one of those countries could have no service at all. In Ginza, this backup system let a single car disable over 10,000 phones for an hour, then send them a fake text message. The default setting is set once, by the phone manufacturers, for all countries at once. Japan got rid of its 2G network years ago, but it doesn't get to decide whether phones in Japan still trust a 2G tower, and they still do.