Secure implementation of SMS registration confirmations?

Question

SMS

Hello,
for one service, you may need to register by phone number, with its confirmation. There are no questions about how to implement the registration itself, but I can’t find information on how to protect myself from intruders. The first thing that comes to mind is multiple registrations to different phone numbers in order to empty the SMS limit or cause financial damage. What are the SMS practices? How does WhatsApp do it for example?

Answer 1

well, I think as an option to check by IP + USER-AGENT + COOKIES, for example, so that you can register 1 time per hour, this is the easiest