What about registrations and authorization by phone number?

Question

Information Security

Questions
1 How can I check if a phone number is fake if there is a service for renting a phone number to receive SMS
2 What about repacha is it necessary if there is authorization via phone

Answer 1

Do not worry about the legality of numbers - this is the problem of mobile operators, the main thing is not to duplicate them. Even if you find out that the number is registered to "Pupkina N.P. passport series number", then you will not know what exactly "Pupkin N.P." enters you codes from SMS. Even the EDS does not give guarantees.
A captcha is needed so that the bots do not register.