SK Telecom offers free SIM cards to customers after data breach

• SK Telecom is now giving away replacement SIM cards
• Earlier in April, it suffered a malware infection in which crooks stole USIM data
• 25 million customers are eligible, but just 6 million will be serviced in May

South Korea’s number one telecommunications provider, SK Telecom, is giving away free SIM cards to 25 million of its customers, after the recent USIM cyberattack. However, due to logistics challenges, it won’t be able to service everyone that fast.

Earlier in April, news broke that SK Telecom suffered a malware infection through which threat actors tried to grab customer USIM information. The attack allegedly happened in mid-April 2025, at night between Saturday and Sunday, when most employees were away for the weekend.

A USIM (Universal Subscriber Identity Module) is the successor of the old SIM card. It’s used in 3G, 4G, and 5G mobile networks and is found in most devices with cellular connectivity.

Booking a slot online

At its core, a USIM authenticates the device’s identity on a network, stores subscriber data (International Mobile Subscriber Identity, authentication keys, contacts, and sometimes text messages), encrypts the information passing through, and enables secure access to mobile services such as calls, data, or texts.

A cybercriminal could use the data to clone the SIM, track people’s location, bypass app security, or eavesdrop on communications.

While the investigation is still ongoing and the number of affected individuals is yet to be determined, SK Telecom announced offering replacement SIM cards to 25 million mobile subscribers, including some two million spilled over from budget carriers. However, it won’t have more than six million units throughout May 2025, which is why the company urged users to book a slot online:

“SK Telecom has blocked the misuse of SIM information with its FDS and SIM protection services, but it still offers a free service for customers who want to replace their SIM card,” reads the machine-translated announcement. “Currently, we have 1 million USIMs, and we plan to secure an additional 5 million SIMs by the end of May. However, it is expected that there will be a large number of customers at once, so please check in advance through the online reservation application system.”

Via BleepingComputer

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