SK Telecom has filed an administrative lawsuit challenging a 134.8 billion won fine imposed by the Personal Information Protection Commission over a USIM hacking incident.

According to the industry on Jan. 19, SKT filed a lawsuit with the Seoul Administrative Court on Monday afternoon seeking to cancel the commission's fine. The deadline to file the administrative lawsuit is Jan. 20.

In August last year, 25 types of information were leaked in a USIM hacking incident at SKT, including mobile phone numbers, international mobile subscriber identity numbers (IMSI) and USIM authentication keys for 23,244,649 users.

The commission imposed a fine of 134.8 billion won and a penalty of 9.6 million won, citing responsibility including inadequate security measures. It is the largest such fine on record, far exceeding the 69.2 billion won fine imposed on Google in 2022 for collecting personal data without user consent and using it for online advertising.

SKT filed the administrative lawsuit on Monday to challenge the decision. A company official said it wants the court to make a close judgment on the commission's fine.

The industry expects SKT to actively highlight factors including that it prepared a compensation plan and an information security innovation plan after the hacking incident, and that there was no financial damage from the leak. It is also expected to question fairness compared with past fine cases involving Google and others.

SKT also received a mediation decision document from the Korea Consumer Agency's Consumer Dispute Mediation Committee on Jan. 16. The committee held a group dispute mediation meeting in December last year and decided SKT should pay compensation worth 100,000 won per applicant.

If compensation is provided to all victims, the total could reach 2.3 trillion won. The industry expects SKT will not accept the mediation plan.

The company said it is closely reviewing the matter.