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SK Telecom's recent data breach — possibly the worst in Korean history — has put much of the country into a panic.
While the country's largest mobile carrier promised to provide free SIM card replacements to all its 23 million customers, those unable to visit a designated store for any reason are growing increasingly concerned about any possible prolonged damage they may be unaware of.
SK Telecom announced Tuesday that some SIM-related information of its users was leaked due to a malicious code by hackers on April 19. After recognizing the leak, SK Telecom reported the incident, deleted the code and isolated the suspected hacking device, according to the company.
Song Gyeong-seop, a 54-year-old resident of Osan, Gyeonggi, spent the past weekend anxious over his elderly in-laws who live about two hours away. His father-in-law, who uses an SK Telecom mobile line, needs to have his mobile SIM card replaced, but both in-laws have dementia and cannot visit a telecom store without family assistance.
“My wife and I both work, so we can’t visit them during weekdays,” said Song. “The telecom store near their home said they will only have stock next week on a weekday, and it’s driving me crazy.”
“I’m already worried every day about them getting phishing calls. If something happens because the USIM replacement is delayed, I don't know what we’ll do,” he sighed.
![An SK Telecom store in Seoul notifies customers that it is out of SIM cards on April 27. [NEWS1]](https://koreajoongangdaily.joins.com/data/photo/2025/04/27/73fb661c-d598-4ade-b3ce-de8011ace961.jpg)
Kim, a 26-year-old graduate student, said, “I have to go to work even on weekends and get off at dawn, so I can’t visit during business hours,” adding, “I’m very anxious, but they don’t even provide proper guidance on what to do.”
Scenes of so-called open runs — people rushing early to stores — are already taking place as subscribers try to replace their SIM cards in advance. SK Telecom announced that customers who replace their SIM cards between April 19 and April 27 will still be eligible for retroactive fee discounts.
On Saturday noon, a small SK Telecom agency in Bongcheon-dong, southern Seoul, was crowded with about 30 customers trying to replace their SIMs.
“I’m too anxious to wait until Monday,” said Lee, a 30-year-old standing in line for over 40 minutes.
In online communities, posts circulated from users saying they had visited telecom stores only to find no SIM cards left in stock.
![A used SIM card held up by an SK Telecom staff on April 25 in Seoul [YONHAP]](https://koreajoongangdaily.joins.com/data/photo/2025/04/27/60efda5b-c9fa-4df6-a616-75530507e203.jpg)
By Sunday morning, signs reading “All available USIMs are out of stock” and “No USIM” were posted at SK Telecom stores across various locations. USIM refers to SIM cards.
A store employee in Mapo District, western Seoul, said, “All 20 USIMs we had left were gone in just one day,” adding, “Normally we order a box of 50 USIMs once every couple of months, so we likely won’t have new stock until early May.”
Frightened subscribers are sharing warnings and countermeasures online. Posts on social media platforms explain that if SIM information is hacked, it could lead to SIM-swapping crimes where bank accounts are drained, urging users to replace their SIMs and subscribe to SK Telecom’s USIM protection service.
Checklists titled “Post-USIM Replacement Security Settings” — including steps like reinstallation and reauthentication on the PASS personal identification app and resetting identity verification for mobile banking apps — have been created and widely shared. The official website of “MSafe,” a mobile identity theft protection service run by the Korea Information & Communication Promotion Association, even experienced temporary slowdowns due to a surge in traffic.
![SK Telecom headquarters in central Seoul on April 22 [YONHAP]](https://koreajoongangdaily.joins.com/data/photo/2025/04/27/829f3b6c-9275-44ec-a8f5-2a68d7cbbabe.jpg)
![SK Telecom CEO Ryu Young-sang, center, bows during a public apology session at the company’s headquarters in Jung District, central Seoul on April 25. [NEWS1]](https://koreajoongangdaily.joins.com/data/photo/2025/04/27/69b30c6b-f725-4748-9eb8-f6d457532a34.jpg)
Major Korean conglomerates such as Samsung Electronics, Hanwha and Posco have issued internal notices instructing executives using SK Telecom networks to take immediate security measures.
Currently, SK Telecom has about 23 million direct subscribers and 1.87 million subscribers using its network via budget carriers, meaning around 25 million people are eligible for the free USIM replacement program.
Critics point out that more support is needed for vulnerable groups such as the elderly or those with limited mobility.
“For now, customers must visit a store in person to replace their USIMs, as personal identification is required," an SK Telecom official said.
Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
BY JUN YUL [yoon.soyeon@joongang.co.kr]
Fear, Anger And Confusion Reign In Wake Of Sk Telecom's Historic Data Breach
Customers wait in line outside an SK Telecom store in Seoul on April 26 to change their SIM cards. [YONHAP]
SK Telecom's recent data breach — possibly the worst in Korean history — has put much of the country into a panic.
While the country's largest mobile carrier promised to provide free SIM card replacements to all its 23 million customers, those unable to visit a designated store for any reason are growing increasingly concerned about any possible prolonged damage they may be unaware of.
Related Article
SK Telecom announced Tuesday that some SIM-related information of its users was leaked due to a malicious code by hackers on April 19. After recognizing the leak, SK Telecom reported the incident, deleted the code and isolated the suspected hacking device, according to the company.
Song Gyeong-seop, a 54-year-old resident of Osan, Gyeonggi, spent the past weekend anxious over his elderly in-laws who live about two hours away. His father-in-law, who uses an SK Telecom mobile line, needs to have his mobile SIM card replaced, but both in-laws have dementia and cannot visit a telecom store without family assistance.
“My wife and I both work, so we can’t visit them during weekdays,” said Song. “The telecom store near their home said they will only have stock next week on a weekday, and it’s driving me crazy.”
“I’m already worried every day about them getting phishing calls. If something happens because the USIM replacement is delayed, I don't know what we’ll do,” he sighed.
An SK Telecom store in Seoul notifies customers that it is out of SIM cards on April 27. [NEWS1]
Kim, a 26-year-old graduate student, said, “I have to go to work even on weekends and get off at dawn, so I can’t visit during business hours,” adding, “I’m very anxious, but they don’t even provide proper guidance on what to do.”
Scenes of so-called open runs — people rushing early to stores — are already taking place as subscribers try to replace their SIM cards in advance. SK Telecom announced that customers who replace their SIM cards between April 19 and April 27 will still be eligible for retroactive fee discounts.
On Saturday noon, a small SK Telecom agency in Bongcheon-dong, southern Seoul, was crowded with about 30 customers trying to replace their SIMs.
“I’m too anxious to wait until Monday,” said Lee, a 30-year-old standing in line for over 40 minutes.
In online communities, posts circulated from users saying they had visited telecom stores only to find no SIM cards left in stock.
A used SIM card held up by an SK Telecom staff on April 25 in Seoul [YONHAP]
By Sunday morning, signs reading “All available USIMs are out of stock” and “No USIM” were posted at SK Telecom stores across various locations. USIM refers to SIM cards.
A store employee in Mapo District, western Seoul, said, “All 20 USIMs we had left were gone in just one day,” adding, “Normally we order a box of 50 USIMs once every couple of months, so we likely won’t have new stock until early May.”
Frightened subscribers are sharing warnings and countermeasures online. Posts on social media platforms explain that if SIM information is hacked, it could lead to SIM-swapping crimes where bank accounts are drained, urging users to replace their SIMs and subscribe to SK Telecom’s USIM protection service.
Checklists titled “Post-USIM Replacement Security Settings” — including steps like reinstallation and reauthentication on the PASS personal identification app and resetting identity verification for mobile banking apps — have been created and widely shared. The official website of “MSafe,” a mobile identity theft protection service run by the Korea Information & Communication Promotion Association, even experienced temporary slowdowns due to a surge in traffic.
SK Telecom headquarters in central Seoul on April 22 [YONHAP]
SK Telecom CEO Ryu Young-sang, center, bows during a public apology session at the company’s headquarters in Jung District, central Seoul on April 25. [NEWS1]
Major Korean conglomerates such as Samsung Electronics, Hanwha and Posco have issued internal notices instructing executives using SK Telecom networks to take immediate security measures.
Currently, SK Telecom has about 23 million direct subscribers and 1.87 million subscribers using its network via budget carriers, meaning around 25 million people are eligible for the free USIM replacement program.
Critics point out that more support is needed for vulnerable groups such as the elderly or those with limited mobility.
“For now, customers must visit a store in person to replace their USIMs, as personal identification is required," an SK Telecom official said.
Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
BY JUN YUL [yoon.soyeon@joongang.co.kr]
