In early 2021, a Telegram bot named “SMSBoomer” amassed over 200,000 users. It allowed anyone to send 300 messages with one click. Researchers found it was abusing 1,200+ legitimate SMS gateways, including those of Walmart, SendGrid, and local police tip lines.
If built-in tools aren't enough, several highly-rated apps specialize in identifying and neutralizing mass-messaging attacks: How to Block Spam Text Messages on Android & iPhone - Avast protection from sms bomber 2021
Protecting yourself from an SMS bomber (or "SMS flood") involves both immediate mitigation during an attack and long-term preventative measures to keep your number out of automated attack lists. Immediate Action During an Attack In early 2021, a Telegram bot named “SMSBoomer”