Multi-Factor Authentication (MFA) relies on proving identity through multiple independent vectors. Traditionally, banks and web services defaulted to sending a One-Time Password (OTP) via cellular text messages (SMS). However, the National Institute of Standards and Technology (NIST) strongly discourages SMS-based MFA because legacy telecommunication networks lack native cryptographic security, making text messages highly vulnerable to interception.

SIM Swapping and SS7 Hijacking

Attackers bypass SMS codes primarily through social engineering. In a SIM Swapping attack, a cybercriminal contacts your cellular provider, impersonating you. By manipulating customer service representatives, they convince the provider to port your phone number to a new SIM card controlled by the attacker. Instantly, all your incoming MFA text messages route directly to the hacker's device, bypassing your security entirely.

Alternatively, advanced threat actors exploit vulnerabilities in the SS7 (Signaling System No. 7) protocol. SS7 is the global routing matrix that allows cell networks to connect. Because SS7 implicitly trusts signaling commands, attackers who gain access to the SS7 network can silently reroute or eavesdrop on SMS traffic over the air without interacting with your physical device or your mobile carrier's retail staff.