Hackers have exploited flaws in the SS7 mobile telephony protocol to hijack phone numbers and SMS messages in order to bypass two-factor authentication (2FA) and steal money from bank accounts. The attacks were reported on Wednesday by German newspaper S..ddeutsche Zeitung, who detailed a first case where cybercriminals exploited known SS7 vulnerabilities for their own profit. The SS7 (Signalling System No. 7) protocol was developed in 1975 and is a so-called telephony signaling protocol used to route calls between different telephony providers.
Source: https://www.bleepingcomputer.com/news/security/hackers-use-flaws-in-telephony-core-protocol-to-bypass-2fa-on-bank-accounts/