SK Telecom 2025 Data Breach
Telecommunications / Mobile Network Operator / Consumer / South Korea
SK Telecom 2025 Data Breach: 27 Million USIM Records Exposed in 3-Year Malware Intrusion
South Korea's largest mobile-network operator.
Confirmed · ObscureIQ Intelligence
Breach Risk Index i
45/100
Lower riskHigher risk
Moderate: notable exposure with meaningful misuse potential.
Data Sensitivity i
StandardExposed data is largely lower-sensitivity. Standard identity-protection precautions are advised.
15k rowsRecords
2025Year
The Breach Risk Index (BRI) is a proprietary 0–100 score rating how dangerous a breach is right now, based on how recently the data has been circulating on the dark web and how valuable it is to attackers.
Breach Summary
On April 19, 2025, SK Telecom detected BPFDoor malware on its network and disclosed that USIM data for about 27 million subscriber numbers was exposed, including phone numbers, IMSI values and device/USIM information. The malware had gone undetected for roughly three years across 23 servers.
Full threat analysis, exploitation vectors, and principal guidance below.
9 additional sections · verified field analysis · defensive doctrine
Querying breach corpus…
Cross-referencing exposed field types…
Resolving threat-actor attribution…
Compiling principal risk advisory…
15k rows records analyzed
About SK Telecom
SK Telecom is South Korea's largest mobile-network operator, serving tens of millions of subscribers.
Why They Hold Your Data
A mobile operator holds subscriber SIM/USIM data including phone numbers and IMSI values, device information and carrier account data.
Recent Developments
SK Telecom detected the malware in April 2025 and later determined the intrusion had persisted for nearly three years; it undertook a mass USIM-replacement program.
Data Points Exposed
3 verified field types
Device Information
Mobile Carrier
Phone Number
Breach Impact
As South Korea's largest carrier, the breach triggered a massive USIM-replacement effort, regulatory scrutiny and national concern over telecom security.
Principal Risk Advisory
What this means for a principal
A telecom breach: subscriber and device data supports SIM-swap, account takeover and location inference. For a high-profile principal the main risk is credible impersonation and enrichment of existing exposure.
What You Should Do
- Guard against SIM-swap and vishing: add a carrier port-out PIN and verify any 'support' calls independently.
- Do not use unofficial 'am I affected' lookups; several are themselves harvesting operations.
How ObscureIQ Can Help
- Corpus confirmation: determine whether and where the principal (plus household and staff) appear in this dataset and which specific fields are exposed for them.
- Exposure mapping and footprint neutralization: cross-reference against broker-available data and suppress still-removable elements, prioritizing address and phone, since this record re-seeds broker networks.
- ThreatWatch tuned to this incident's identifiers and misuse pattern (impersonation and targeting patterns, not generic credential monitoring).
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