South Korea: SK Telecom hit by cyber attack, risk of important data leak

According to South Korea's Yonhap news agency, on May 19, a joint investigation team between the government and the private sector of the country said that the server of South Korea's largest telecommunications group SK Telecom, which contains personal information and USIM (3G network phone SIM) data of all users, was hacked in a cyber attack.

This raises concerns about the possibility of leaking important USIM data used in financial transactions.

According to preliminary investigation results, the intrusion began on June 15, 2022, when unknown hackers are believed to have installed malicious code on the company's server system.

A total of 23 SK Telecom servers were compromised. All of them stored four types of key USIM data, including IMSI (international mobile subscriber identity) information. This is a unique identifier for each user on the network that can be exploited to conduct financial transactions.

Investigators say it is likely that 9.32 Gb of USIM data, equivalent to about 26.9 million IMSI codes, was leaked.

SK Telecom currently has 25 million subscribers, including about 2 million users of low-cost plans. Among the affected servers, two were used as temporary storage for personal data such as names, dates of birth, phone numbers and email addresses. Investigators are still verifying the extent of personal data stored on these two servers.

The investigation team said it found no evidence of a data breach occurring between December 3, 2024 and April 24, 2025, based on firewall logs left behind by the hackers.

However, a worrying information gap exists as no data logs were recorded between June 15, 2022 and December 2, 2024, making it impossible to confirm whether a data leak occurred during this period.

SK Telecom discovered the attack on April 18. To fix it, the company offered to replace USIMs for free for all 25 million subscribers, including 2 million users of low-cost plans, to prevent identity theft or financial fraud.

In addition, the group has also automatically registered USIM protection service for all users to prevent unauthorized financial activities./.

(Vietnam News Agency/Vietnam+)

Source: https://www.vietnamplus.vn/han-quoc-sk-telecom-bi-tan-cong-mang-nguy-co-ro-ri-du-lieu-quan-trong-post1039390.vnp