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SK Telecom USIM data breach

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Made public · 23,244,649 people

What leaked9

Replaceable

  • SIM authentication key
  • IMSI

Hard to replace

  • Phone IMEI
  • Mobile number
  • Home or delivery address
  • Email address
  • Other profile data

Permanent

  • Date of birth
  • Full name
  • SIM authentication keyKi, OPc
  • Phone IMEItemporarily stored on the infected ICAS servers; whether it leaked between June 2022 and December 2024 could not be determined · PIPC
  • Other profile dataother internal fields: 25 items in total per PIPC · SKT's own notice listed 21

To-dos10 · about 2 h in all

  1. Block carrier billing or lower its limitabout 5 minStops: carrier billing
  2. Turn on the carrier's USIM protection serviceabout 3 minfreeLimits harm from: carrier billing, SIM swap
  3. Replace the USIM or reissue the eSIMabout 30 minLimits harm from: carrier billing, SIM swap
  4. Know the scam pattern: calls and texts that cite these leaked detailsabout 5 minfreeLimits harm from: scam calls, phishing messages
  5. Block open banking at banks you chooseabout 10 minLimits harm from: scam calls, SMS code theft (opens in a new tab)
5 more
  1. This weekBlock new mobile lines in your name with Msaferabout 10 minfreeLimits harm from: SIM swap (opens in a new tab)
  2. This weekRegister as an exposed person with the FSSabout 10 minLimits harm from: scam calls (opens in a new tab)
  3. This weekBlock new loans and cards in your nameabout 10 minLimits harm from: scam calls (opens in a new tab)
  4. This weekRemove your address and phone from public profiles and tighten SNS privacyabout 20 minfreeLimits harm from: visits or contact at home
  5. When convenientUse an authenticator app or passkey instead of SMS codesabout 20 minfreeLimits harm from: SMS code theft

What happened next57 events

  1. Undetected 2 eventsabout 3 yr 8 mo · Back to latest
  2. Response 25 eventsNotice in 21 days · show events
  3. Remedy 7 eventsEnded · show events
  4. Penalty 15 eventsFine ₩134.8B · show events
  5. Disputes 8 eventsOngoing · show events

Undetected: 2 events

Back to latest
  1. SK Telecom noticed unusually large data transfers leaving its network at 23:20
  2. Intrusion began
Company
SK Telecom
When it happened
–
Company detected it
Made public
Notice
Leak confirmed
Affected
23,244,649 people · LTE/5G incl. MVNO, deduplicated; PIPC; 26.96M records by IMSI · MSIT

How the facts developed

  1. PIPC decision: 23,244,649 people; 과징금 1,347억 9,100만원, 과태료 960만원 (72-hour notice missed)
  2. MSIT final result: 25 items, 9.82 GB; IMEI and some identity fields possibly exposed, not verifiable
  3. Site-wide notice of a presumed partial leak; May 2, 2025 PIPC ordered statutory notification to everyone possibly affected, including MVNO subscribers; individual notices May 9, 2025

Sources