SK Telecom USIM Data Breach: Massive Hacking Attack and Its Fallout

In April 2025, SK Telecom, South Korea’s largest telecom provider, suffered a massive security breach. Hackers infiltrated the company’s core subscriber system and stole sensitive USIM authentication data, potentially affecting tens of millions of users. This incident is now considered one of the worst telecom data breaches in South Korean history, exposing deep issues in security infrastructure, corporate transparency, and market concentration.

📌 Incident Summary

• Hacking of SKT’s Home Subscriber Server (HSS) → USIM keys stolen
• High risk of SIM cloning and identity theft
• Company delayed reporting the breach by over 40 hours
• CEO issued a public apology and initiated compensation efforts

🔍 Critical Perspectives

• Slow response and lack of transparency damaged public trust
• Oligopolistic telecom structure criticized for lack of accountability
• Confusion between regulators hindered effective oversight

This episode dives deep into the full scope of the SKT breach, its technical and political implications, and what it reveals about South Korea’s telecom industry.