BUSAN — Police have broken up a network that smuggled, distributed and operated relay devices that disguised internet calls from overseas as domestic Korean mobile numbers beginning with "010," along with the people who supplied them with SIM cards registered under their own names. The group recruited foreign nationals of multiple nationalities through Telegram and operated as isolated cells with no face-to-face contact, but investigators cracked the case by tracing SIM card fragments discarded in a drain.
The Busan Metropolitan Police Agency's narcotics and international crime investigation unit said on the 20th that it had arrested 101 people, including members of the distribution and operating network and the SIM card suppliers, on charges of violating the law on refunds for telecommunications fraud damages and the Telecommunications Business Act. Sixteen of them, including the head of distribution and couriers who delivered the equipment, were detained. Police also seized 400 relay devices, 121 phones registered under other people's names, 5,256 SIM cards and 848 pieces of equipment including routers.
According to police, the group smuggled the relay devices into the country disguised as hard drives between November last year and September this year, then installed and operated them in studio apartments and other locations to support phishing operations run by overseas fraud rings. The devices converted the caller ID of internet calls placed from abroad into domestic "010" numbers. The SIM card suppliers were found to have activated subscriptions in their own names and handed them over in exchange for 60,000 to 120,000 won each, or in some cases to obtain loans.
Nineteen people were defrauded in phishing schemes in which callers impersonated prosecutors using the relay equipment supplied by the group, with losses totaling 1.5 billion won, police confirmed.
The investigation began in February with a tip that a large number of SIM card fragments had been found in a drain at a studio apartment building in Busan. After confirming that the SIM cards had been used in phishing calls impersonating prosecutors, police analyzed the site and nearby closed-circuit television footage to identify the person running the relay devices. Questioning that suspect and tracing the routes through which the equipment and SIM cards were delivered led police to arrest the head of distribution, recruiters and couriers one after another.
The network divided its work from the point of entry into the country through domestic distribution, installation and operation. Police said the overseas ringleader and the smugglers were Chinese nationals, while most of the members handling domestic distribution and operations were nationals of Russia, Belarus, Kazakhstan and Uzbekistan. They were recruited through job boards on Telegram and operated as isolated cells, each active only within the scope of an assigned role. Equipment was passed along by leaving it at drop points rather than through direct handoffs.
Police searched two warehouses and the residences of suspects to secure the equipment used in the crimes. Police said the significance of the investigation lay in using the SIM card fragments found in the drainpipe as a lead to track down not only those operating the devices on site but also the network that distributed and supplied the equipment, cutting off the infrastructure behind the phishing operations.
The Busan police said they would continue to pursue the identities and whereabouts of additional members and the overseas ringleader, the routes by which the relay devices entered the country, and the proceeds of the crimes. "Do not assume a call is domestic just because the number appears as '010,'" a police official said. "If someone claiming to be from a law enforcement agency demands a wire transfer or a cash handover, hang up and verify through an official contact number. Activating a SIM card in your own name and handing it over for payment can also be exploited in phishing crimes."