We faced this at my last company and this is actually a super mild case. In our case, we were dealing with call toll fraud. We ended up with tens of thousands of dollars in charges in less than 24 hours.
In our case, Twilio reached out to us to tell us they were detecting toll fraud. Before that, we actually had no idea what toll fraud was.
We quickly tried to address it with distributed rate limiting and that worked, for all of a couple of hours. The fraudsters quickly figured out the rate limit and worked around it by spacing out the calls and using more IPs.
Eventually, we had to disable a set of countries known for toll fraud and change our product to not connect calls in a variety of scenarios.
In our case, Twilio reached out to us to tell us they were detecting toll fraud. Before that, we actually had no idea what toll fraud was.
We quickly tried to address it with distributed rate limiting and that worked, for all of a couple of hours. The fraudsters quickly figured out the rate limit and worked around it by spacing out the calls and using more IPs.
Eventually, we had to disable a set of countries known for toll fraud and change our product to not connect calls in a variety of scenarios.