SK Telecom warns customer USIM data exposed in malware attack

HELLFIRE

https://www.bleepingcomputer.com/news/security/sk-telecom-warns-customer-usim-data-exposed-in-malware-attack/

South Korea’s largest mobile operator, SK Telecom, is warning that a malware infection allowed threat actors to access sensitive USIM-related information for customers. SK Telecom is the largest mobile network operator in South Korea, holding approximately 48.4% of the mobile phone service market in the country, corresponding to 34 million subscribers. The company says they detected malware on their systems at 11 PM local time on Saturday, April 19, 2025, in a weekend cyberattack when most organizations are understaffed. “Once we became aware of the possible leak, we immediately deleted the malware and isolated the equipment suspected of being hacked,” reads the security notice. … USIM data is information stored on a Universal Subscriber Identity Module (USIM), which typically includes International Mobile Subscriber Identity (IMSI), Mobile Station ISDN Number (MSISDN), authentication keys, network usage data, and SMS or contacts if stored on the SIM. …

Regards

px_eliezer_

HELLFIRE The company says they detected malware on their systems at 11 PM local time on Saturday, April 19, 2025, in a weekend cyberattack when most organizations are understaffed.

The law should require crooks to take the weekends off. /s

Seriously, there should be as much or even more alertness on weekends or holidays.

HELLFIRE

https://www.bleepingcomputer.com/news/security/sk-telecom-cyberattack-free-sim-replacements-for-25-million-customers/ – SK Telecom cyberattack: Free SIM replacements for 25 million customers

South Korean mobile provider SK Telecom has announced free SIM card replacements to its 25 million mobile customers following a recent USIM data breach, but only 6 million cards are available through May. … In an update published earlier today, SK Telecom assured customers that such requests would be automatically detected and blocked by its Fraud Detection System (FDS) and SIM Protection Service, which have been enhanced to handle the elevated risk. As of today, SK Telecom is also offering free-of-charge SIM card replacements to 25 million mobile subscribers, including approximately 2 million using budget carriers, who are worried about the potential for SIM swapping attacks impacting them. However, the mobile carrier warns that due to a lack of inventory, they can only replace up to 6 million SIM cards through May 2025. …

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HELLFIRE

https://www.bleepingcomputer.com/news/security/sk-telecom-says-malware-breach-lasted-3-years-impacted-27-million-numbers/ – SK Telecom says malware breach lasted 3 years, impacted 27 million numbers

SK Telecom says that a recently disclosed cybersecurity incident in April, first occurred all the way back in 2022, ultimately exposing the USIM data of 27 million subscribers. … The telecom firm mentions that it identified 25 distinct malware types in 23 compromised servers, so the extent of the breach is far more extensive than initially anticipated. …

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HELLFIRE

https://www.theregister.com/2025/08/28/sk_telecom_regulator_fine/ – SK Telecom walloped with $97M fine after schoolkid security blunders let attackers run riot
https://www.pipc.go.kr/np/cop/bbs/selectBoardArticle.do?bbsId=BS074&mCode=C020010000&nttId=11453

… The carrier tried to mitigate the fallout by offering free SIM replacements to affected customers, but regulators smelled something bigger and launched a full-blown probe into the leak. The Personal Information Protection Commission (PIPC) said that the country’s biggest carrier “did not even implement basic access controls” between its internet-facing systems and internal management network. As a result, attackers were able to infiltrate SKT’s core systems, extract authentication data, and siphon off subscriber information at scale. … According to the regulator’s report, SKT failed at almost every layer of defense. …

What’s the South Korean equivalent of “Holy S**T!” ? Asking for a friend… 🙄 🙄

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