Hackers with access to the Signaling System 7 (SS7) used for connecting mobile networks across the world were able to gain access to Telegram messenger and email data of high-profile individuals in the cryptocurrency business. The attack occurred in September and targeted at least 20 subscribers of the Partner Communications Company (formerly known as Orange Israel), all of them involved at a higher level in cryptocurrency projects. The hackers were after two-factor authentication (2FA) login codes delivered over the short messaging system of victim s mobile phone provider.
Source: https://www.bleepingcomputer.com/news/security/hackers-hijack-telegram-email-accounts-in-ss7-mobile-attack/