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SK Telecom Cyberattack Exposes Data of 26.9 Million Subscribers

A joint investigation confirms a three-year breach involving 23 servers, leaking sensitive USIM and personal data, with forensic analysis ongoing.

This file photo taken on April 22, 2025, shows the company's headquarters in Seoul. (Yonhap)
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This illustration highlights universal subscriber identity module (USIM) chips. (Yonhap)
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Overview

  • The breach, undetected since June 2022, compromised 23 SK Telecom servers, exposing 9.32 GB of USIM data, equivalent to 26.9 million IMSI entries.
  • Investigators confirmed 291,831 IMEI numbers were exposed, raising concerns about device cloning risks, though manufacturers state cloning requires additional encryption keys.
  • Two servers temporarily stored personal data, including names, birthdays, phone numbers, and email addresses; the full scope of this data is still under review.
  • SK Telecom has offered free USIM replacements for 25 million subscribers and enrolled all users in a USIM protection service to mitigate fraud risks.
  • Forensic analysis on 15 of the 23 infected servers has been completed, with the remaining eight servers expected to be analyzed by the end of May.