Sam is assessing risks to her multifactor authentication system. Which of the following is the most likely threat model against short message service (SMS) push notifications to cell phones for her environment?

As Sam is specifically concerned about SMS pushes to cell phones, the most likely attack model is SIM (subscriber identity module) cloning, allowing attackers to obtain the authentication codes sent to legitimate users. Attacks on a Voice over Internet Protocol (VoIP) system would typically help intercept SMS if it was sent to VoIP phones, not cell phones (although forwarding is possible, but not mentioned here). Brute-force attacks are unlikely to succeed against SMS phone factors, and rainbow tables are used to crack hashed passwords.