Telcos in Hong Kong are now required to indicate whether a call is coming from overseas by inserting a plus sign in front of numbers originating from outside the city.
The move is part of the government's effort to crack down on phone scams plaguing the city.
"There has been a surge in phone scams lately involving scammers deliberately changing or falsifying the caller ID by means of caller ID spoofing," a Commerce and Economic Development Bureau spokesman told the South China Morning Post (SCMP). "The police indicated that these phone scams originate from outside Hong Kong."
According to the police, 39 residents were cheated a total of HK$56.72 million in the first 14 days of this month. Last month, HK$126 million was lost to cross-border phone scams, with some of the money remitted to Malaysia, Taiwan and Macau.
In a typical scam, a Putonghua or Cantonese-speaking fraudster calls a victim to inform that they have infringed a mainland law. They will then be directed to a fake government website showing a forged arrest warrant, and asked to prove their willingness to cooperate by transferring money to a mainland bank account.
Since the mandatory plus sign in front of a phone number indicates that the callis from abroad, it would help Hong Kong residents decide whether or not to pick up a call, said the spokesperson. "If the person decides to take the call, he or she should remain vigilant and be on guard against possible telephone scams. They should [always remember to] not disclose their personal information to, or accede to any request of, a dubious caller."
While this security measure is a good attempt at preventing phone scams and weeding out the scammers, it is not foolproof. Kaibin Huang, a University of Hong Kong wireless network expert, told SCMP that the move could be bypassed through rogue base stations. "Rogue base stations can serve as agents for scam calls from outside the city [and] unfortunately they can now be purchased from illegal markets at relatively low prices."
He explained that scammers could use fake base stations to manipulate phones and send false caller identification to trick call recipients into trusting the station as genuine.
However, a spokesperson for the Office of the Communications Authority of Hong Kong said that if such illegal base stations are installed in Hong Kong, they can be easily tracked down by the authorities.
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