Is SMS verification code really safe?

I'm going to say that nothing is absolutely safe, but security protection really needs attention, and SMS verification code is not the safest authentication method. The reason why SMS authentication can grow wildly in a few years is that on the one hand, it is the lowest cost, the simplest and most convenient authentication method for SMS secondary authentication, on the other hand, the popularity of mobile phones is also the most easily accepted by the majority of users, and the security of SMS authentication is also relatively high.