Why SMS is not a secure Multi-Factor Authentication (MFA) method

Multi-factor authentication (MFA) is a crucial defense against account compromise, but SMS-based MFA is inherently flawed and poses significant security risks. Vulnerabilities such as SIM swap attacks, lack of end-to-end encryption, and susceptibility to phishing make SMS MFA inadequate for securing sensitive data. Additional issues include the reliance on unstable phone numbers and the insecure mobile carrier infrastructure. Recognizing these weaknesses, security authorities like NIST have deprecated SMS as a secure MFA method since 2017, recommending more secure alternatives. Major platforms and security-conscious enterprises now prefer stronger MFA methods such as authenticator apps, push notifications, and hardware security keys, which provide greater resilience against phishing and do not depend on mobile networks. As security expectations rise, relying on SMS MFA could undermine the security posture of applications, prompting organizations to transition to more robust authentication solutions.