SK Telecom: April 2025 USIM data breach, record privacy fine and a pending court challenge
SK Telecom: April 2025 USIM data breach, record privacy fine and a pending court challenge: a public-record watch file compiled by Falling Shares Intelligence from filings and exchange disclosures, as of 2026-11-09. SK Telecom detected a large volume of data leaving its network on 18 April 2025 and reported the USIM breach to the privacy regulator on 22 April.
From the April 2025 USIM breach to a negligence finding, a record KRW 134.8bn privacy fine, a rejected compensation proposal and a court challenge still under way.
Falling Shares Intelligence, Edited by Wung Thomas, Editor-in-Chief. As of .
Summary
- SK Telecom detected a large volume of data leaving its network on 18 April 2025 and reported the USIM breach to the privacy regulator on 22 April.
- A joint government investigation in July 2025 found the company negligent; in August 2025 the Personal Information Protection Commission fined it KRW 134.8bn, the largest it has imposed on one company.
- SK Telecom sued to overturn the fine in January 2026 and rejected a consumer-agency compensation proposal; the case was before the court in September 2026.
Key figures
| Privacy fine | KRW 134.8bn (Plus a KRW 9.6m penalty for late notification) |
|---|---|
| Users affected | More than 23m (Phone numbers, IMSI and other USIM data, per the regulator) |
| Company package | KRW 1.2tn (Compensation and security spending as described by the company and reports) |
| Proposed compensation | KRW 100,000 per user (Consumer-agency mediation proposal, Dec 2025) |
The breach and the government findings
Breach detected and reported
SK Telecom detected a large volume of data leaving its network on 18 April 2025 and reported the breach to the privacy regulator on 22 April. The regulator later said phone numbers, IMSI numbers and 23 other types of USIM data of more than 23 million users were compromised. (18-22 Apr 2025)
Joint investigation finds negligence
A joint government and private team led by the Ministry of Science and ICT concluded that SK Telecom failed to fulfil its duty of care to protect USIM data and did not comply with relevant rules. The ministry ordered quarterly security measures, direct oversight of data governance by the chief executive and more security staff and spending, and set a fine of up to KRW 30m. (4 Jul 2025)
Termination fees waived
Following the negligence finding, the ministry said early-termination penalties should be waived for contract customers who cancelled between 19 April and 14 July 2025. SK Telecom accepted the waiver. (Jul 2025)
Regulator fine and customer compensation
Privacy regulator imposes a record fine
The Personal Information Protection Commission fined SK Telecom KRW 134.8bn, the largest fine it has imposed on a single company, plus a KRW 9.6m administrative penalty for late notification. It cited weak access control, poor management of access rights, failure to encrypt USIM authentication keys and delayed notification of users, and ordered a system-wide inspection and a governance overhaul. (27-28 Aug 2025)
Consumer agency proposes KRW 100,000 per user
The Korea Consumer Agency's dispute mediation proposed KRW 100,000 per user, made up of a KRW 50,000 fee reduction and KRW 50,000 in credits. The mediation followed an application by 58 consumers in May 2025, and acceptance by SK Telecom would have extended compensation to others affected. (21 Dec 2025)
Company response and court challenge
Company package announced
SK Telecom announced about KRW 700bn of data-protection spending over five years and a KRW 500bn customer plan, including a 50% discount on August subscription fees and free USIM replacement. (Jul 2025)
Company rejects mediation proposal
SK Telecom rejected the consumer agency's compensation proposal, so the mediation ended unresolved and applicants would have to pursue separate civil claims. (Jan 2026)
Company sues to overturn the fine
SK Telecom filed suit in the Seoul Administrative Court the day before the deadline, asking for a thorough review of the fine. It was reported to plan to cite its KRW 1.2tn of compensation and protection spending and the absence of confirmed financial harm to users. A trade report said the case reached its first oral hearing in September 2026. (19 Jan 2026)
Standard
This file compiles regulator decisions, court filings as reported, company statements and published reporting about SK Telecom Co., Ltd.. Allegations are attributed to those who made them. An investigation is not a charge, a charge is not a finding, and nothing here is a finding of wrongdoing unless a competent authority has made one. The privacy regulator and the science ministry have made findings against SK Telecom, which is contesting the fine in the Seoul Administrative Court. Individuals are not named unless an official document names them and they are central; otherwise roles are used. This is news coverage for information only, not investment advice.
Right of reply
SK Telecom Co., Ltd., and anyone named in a record cited here, can send corrections or comments to info@fallingshares.com (or directly to the Editor-in-Chief, Wung Thomas, at wungthomas@fallingshares.com). Material responses will be published alongside the relevant entry.