> Ask HN: How can scam callers fake a mobile phone number? International Telephone Standards. VoIP VoIP Companies like https://www.sipgatebasic.co.uk/tour http

> Ask HN: How can scam callers fake a mobile phone number? International Telephone Standards. VoIP VoIP Companies like https://www.sipgatebasic.co.uk/tour https://www.sipgatebasic.co.uk/tour And if you set up a VoIP number and a pbx like freeswitch or asterisk, they will send the ringing tones down to the caller so if you have the pbx set to record calls you can listen to what the caller is chatting about whilst they are ringing you, hearing the ringing tone at their end waiting for you to pick up. All a bit spooky but thats the technology for you! > - How can a spam caller call me with a source phone number that does not exist? Again they have the VoIP number but when you ring it they can play a dead line tone down to you instead or a ringing tone. With VoIP and Freeswitch/asterisk and probably other PBX's you control all of that. > - Shouldn't my mobile phone network verify that the caller - which was also inside their network - is a valid subscriber? Otherwise, how can they bill someone for this call? Depends on the telecoms standards in the country and/or the telecoms provider. > - How does this kind of scam call work technically? Any member of the public can set up VoIP number and PBX's like freeswitch and asterisk and do this. If its not a VoIP then telecoms companies and the security services in your country, or maybe you mobile phone is hacked and your mobile has logged onto a local fake cell instead which is slightly different to the VoIP setup above but I dont know how much this device can do. https://en.wikipedia.org/wiki/Stingray_phone_tracker#Active_(cell_site_simulator)_capabilities https://en.wikipedia.org/wiki/Stingray_phone_tracker#Active_... and you can do things like this https://www.wired.com/2010/07/intercepting-cell-phone-calls/ https://www.wired.com/2010/07/intercepting-cell-phone-calls/