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Ask HN: How can scam callers fake a mobile phone number?

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Re: Ask HN: How can scam callers fake a mobile phone number?

#121

Post by tonfreed »

sschueller wrote: post #97
TACIXAT wrote: post #60

It is actually incredibly easy! If you are using a voip line, it is just a configurable field in the UI. You can do it with any voip phone app (e.g. [1]) and a voip provider (e.g. [2]). I have an old archived video showing it here [3]. It is not so interesting though, just me poking around in a voip provider's UI. To address the other question about phone providers verifying stuff. SHAKEN/STIR [4] protocols are suppo…

It's ridiculous that phone companies allow this. Anyone wanting to set caller ID via voip should be forced to provide some sort of verification that the number is theirs and the phone company should not route it if it fails verification. We only have 3 major cell carriers here is Switzerland, it should be trivial for the 3 to verify each other's numbers to see if those customers even exist. Unlike the US each cell pr…

Welcome to the wonderful house of cards that is the SIP protocol

Re: Ask HN: How can scam callers fake a mobile phone number?

#123

Post by lattalayta »

marckemil wrote: post #93
mef wrote: post #38

Earlier quoted context omitted.

on iOS, the "Silence Unknown Callers" feature has completely eliminated this for me.

Canadian physician here: yeah, this is hell for us trying to reach patients through the hospital system, which is "unknown" by default. Straight to voicemail and you can't really leave a message. Totally agree though, this problem is very time consuming, if only for the time it takes me to look at my phone and decide not to answer the call - a few seconds of my life each time. My worst day was a few days ago; 7 calls…

Out of curiosity - what do you mean by "Can't really leave a message" ?

Re: Ask HN: How can scam callers fake a mobile phone number?

#124

Post by Terry_Roll »

> Ask HN: How can scam callers fake a mobile phone number?

International Telephone Standards. VoIP VoIP Companies like 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_...

and you can do things like this https://www.wired.com/2010/07/intercepting-cell-phone-calls/

Re: Ask HN: How can scam callers fake a mobile phone number?

#125

Post by exabrial »

bufferoverflow wrote: post #69
downrightmike wrote: post #7

Caller id is just a user settable field. There are two numbers, ANI which is how telcos are supposed to keep track of who to charge. NO one uses it, because users don't like it. And caller id is sent out on the second ring, but again, user can set that to anything. Corps have to adhere to the TCPA, others don't and SIP calls are cheap and globally routable. https://www.fcc.gov/sites/default/files/tcpa-rules.pdf

That's a ridiculous system design.

You're correct, but back in the day, all nodes were trusted nodes, so would have been a lot of overhead to authenticate all this stuff. Hasty regulatory oversight in a fledgling industry led to the current situation.

STIR/SHAKEN actually has the potential to do things correctly, as a call Digital Attestation Certificate has to be supplied... but telcos make quite a bit of money off of scam callers so don't expect them to move quickly, and I'd expect them to implement it in the absolutely poorest way possible.

Re: Ask HN: How can scam callers fake a mobile phone number?

#126

Post by jamal-kumar »

b112 wrote: post #111
jamal-kumar wrote: post #40

Back in the day you used to be able to spoof caller ID using in-band signalling. it was like a few fun sounding handshake tones and some static-sounding data that you would play after the official one, and that was called orange boxing. That was the Bell 202 FSK signal and I remember hearing it on landlines up until a decade ago if the phone was picked up as soon as it started ringing. In Canada caller ID also includ…

Again only crazy people give me actual phone calls anymore I was going to say "Wait!", but then realised all my calls were from recruiters and HR departments. So I guess you're right.

For me they always want to set up a zoom call nowadays

Re: Ask HN: How can scam callers fake a mobile phone number?

#127

Post by xad6 »

bufferoverflow wrote: post #69
downrightmike wrote: post #7

Caller id is just a user settable field. There are two numbers, ANI which is how telcos are supposed to keep track of who to charge. NO one uses it, because users don't like it. And caller id is sent out on the second ring, but again, user can set that to anything. Corps have to adhere to the TCPA, others don't and SIP calls are cheap and globally routable. https://www.fcc.gov/sites/default/files/tcpa-rules.pdf

That's a ridiculous system design.

Similar to the original SMTP implementation, it was designed in an era where folks often assumed that only "trusted parties" had access to the network backbone (whether that network is circuit-switched or packet-switched).

Re: Ask HN: How can scam callers fake a mobile phone number?

#128

Post by martyvis »

lattalayta wrote: post #123
marckemil wrote: post #93

Earlier quoted context omitted.

Canadian physician here: yeah, this is hell for us trying to reach patients through the hospital system, which is "unknown" by default. Straight to voicemail and you can't really leave a message. Totally agree though, this problem is very time consuming, if only for the time it takes me to look at my phone and decide not to answer the call - a few seconds of my life each time. My worst day was a few days ago; 7 calls…

Out of curiosity - what do you mean by "Can't really leave a message" ?

Not the OP, but if you are a doctor and need to ring a relative or a friend to inform them about a very sick patient, leaving a message without the opportunity for at least brief interaction isn't something particularly pleasant for either party. ( You either leave too nonspecific information that not being sure what to do, or too much that potentially is breaching patient confidentiality or is going to panic the recipient)

Re: Ask HN: How can scam callers fake a mobile phone number?

#129

Post by philovivero »

brk wrote: post #29
bombcar wrote: post #12

This is why I like having my number from where I lived in 2005 (see https://xkcd.com/1129/ ) - any calls from "my area code" are automatically spam unless it is a particular number I know.

This is the same thing for me. Short version is that I'm from Detroit area, lived in NH for a while, and now reside in Tampa area. My cellphone has a 603 area code (NH). But since I'm not from there, the only 603 numbers I care about are already in my address book, any others are guaranteed to be spam calls. This lets me easily ignore 95% of them (I also occasionally see an 802 (VT) number or a 978 (MA) number). What…

I get scam phone calls with area codes from most of the major metro areas all over the USA although since it's a California area code, it seems most are from somewhere in California.

Your final paragraph is pretty on-point.

> It is somewhat amazing how the telco's have let their core product, voice calls, become nearly worthless by not handling these spam call problems

I have more than once thought about just giving up on having a phone number at all. Unfortunate that isn't an option yet.

Re: Ask HN: How can scam callers fake a mobile phone number?

#130

Post by winternett »

I hate to sound like a conspiracy theorist, but it's pretty easy for a carrier to determine devices that are making spam calls because they log everything, and they could simply create and distribute apps to their customers to enable reporting of spam calls, but somehow for years they've left it up to dodgy 3rd party app providers and the calls keep rolling.

I don't think carriers have any incentive to stop spam calls because they gain a lot of money every year in billing minutes for those spam calls (mostly prepaid accounts are affected by the billing unfortunately)...

I wouldn't dare go as far to say that the calls are possibly even sponsored or conducted by profiteers in the game... (People who sell prepaid and metered phone services)

Just a personal opinion though.

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