Biggest Data Breaches in Telecommunications (Updated September 2026) | UpGuard

This report ranks and analyzes the 32 largest telecommunications breaches up to September 2026, highlighting Salt Typhoon as the most consequential espionage campaign for its persistent access to routing and lawful-intercept systems; it documents large-scale metadata and identity-data exfiltrations (e.g., AT&T Snowflake, T‑Mobile, Optus, SK Telecom), supply‑chain and third‑party failures (Accellion, Syniverse, Snowflake tenants), exploitation of unpatched edge devices and zero-days, and common attacker techniques (credential theft, infostealers, cloned SIM/USIM keys). The report also outlines regulatory impacts across jurisdictions and promotes continuous external monitoring (UpGuard) to detect exposed edge devices, leaked credentials, and risky third parties.