In 2023, SMS pumping was put on everyone's radar when X (formerly Twitter) announced that it was being scammed $60 million annually through phone companies by SMS pumpers. SMS fraud is a worldwide plague perpetuated by sophisticated and highly organized criminal groups. Their goal is to generate as much revenue as possible by sending SMS messages through foreign carriers that pay the fraudsters a commission, without getting caught. Fraudsters use bots and fraud farms to create fake accounts at sites where they find vectors to pump SMS messages to lists of mobile phone numbers they have obtained. With SMS OTP increasing in popularity as an authentication factor, it has also become a prime target of SMS fraud in countries with carriers that pay fraudsters SMS commissions. Businesses sending the messages often don’t realize they are a target until it’s too late, usually because bills have increased dramatically in a short period of time. In this session, we'll explore how Yahoo successfully confronted and thwarted SMS pumping fraud.