It's not just twilio. Anyone with a direct connection (ISDN, T1/T3 etc) to a telco can spoof caller ID. There are also thousands of SIP phone providers and you

It's not just twilio. Anyone with a direct connection (ISDN, T1/T3 etc) to a telco can spoof caller ID. There are also thousands of SIP phone providers and you can spoof caller ID from almost all of them- I've done it and you need nothing more than a SIP account and Astersik. It would be trivial to build a robodialer that could cycle through hundreds of SIP accounts using trials, hacked accounts and stolen credit cards. You could put it on a VPS created using a stolen credit card and be un-traceable. Or, you could just do what everyone else does and locate yourself overseas, in a country with weak laws.