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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?

#91

Post by xwdv »

throwawayboise wrote: post #76
xwdv wrote: post #70

Earlier quoted context omitted.

It is, and you must set aside your personal feelings and treat it as public info. If people think these digits are like some secret password, they will be treated as such and used to gatekeep access to even more restricted info and accounts. Which would be a disaster because many people have had these last four digits exposed over time. Knowing them does not prove identity. They are public.

You might as well assume your entire SSN is public. Most of them have been leaked someplace or other, and for anyone who was an adult before about 2000 it was common to have them pre-printed on your personal checks. It's only in the past few decades that they have suddenly become "secret." That someone who called you on the phone happens to know your SSN last four or even the entire number should not confer any trust…

The second you believe your SSN represents privileged information, that’s when you get taken advantage of.

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

#92

Post by cryptonector »

bigmattystyles wrote: post #71
cryptonector wrote: post #46

Signalling system 7 has no authentication. That's the bottom line. Adding authentication is pretty obviously not trivial, not just because of protocol upgrade issues, but also because end-to-end authen. won't be easy to add at all, and hop-by-hop authen. w/ something like "egress filtering" won't work in the age of phone number portability. What might work is a TCP-like return routability test. I.e., have the network…

What about charging a penny or 5cents per call? Nominally cheap for regular users, would put a dent in scammers. And don’t let the phone company keep the money, put it towards the infrastructure.

Billing is one of the highest costs for telcos.

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

#93

Post by marckemil »

mef wrote: post #38
ghostpepper wrote: post #30

I live in Canada, and I and most people I know receive spam calls from spoofed numbers on a semi-regular basis. Sometimes the number only a few digits off from my number, but other times it has a name like TOLL FREE SERV. A common lure is claiming they are Service Canada or Canada Revenue Agency (or the nonexistent Revenue Canada), and the call will open with nonsensical threats like “A warrant has been placed in you…

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.

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

#94

Post by mullen »

jmholla wrote: post #58
pxx wrote: post #44

Earlier quoted context omitted.

You can do this in software on your phone (assuming Android).

How does one do that? Do I need another app? I don't see a setting for this in my Android settings.

In the Phone App, under Settings -> "Spam and Call Screen", there are bunch of Spam and Call Screening options.

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

#95

Post by gojomo »

xwdv wrote: post #63
localhost wrote: post #24

Earlier quoted context omitted.

I remember many years ago getting a random phone call from someone who claimed they were a detective investigating a case. The detective sensed my skepticism right away over the phone and suggested that I look up the phone number for his police department, and to ask for badge number ZZZ when I call. I called back, everything was above board, they came and interviewed me (they wanted to see if I still had something i…

All this could be faked, this could have been an elaborate scam.

Yes, if the stakes were large enough, & the adversary sufficiently skilled/resourced, it is possible an impersonator could also intercept & redirect your call to "the police" – for example by compromising phone network systems or the police-department's switchboard. (Or, somehow corrupt your usual means of looking up that police number.)

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

#96

Post by jonsen »

hungryforcodes wrote: post #51
noneeeed wrote: post #45

Earlier quoted context omitted.

Also, if you were rung on a landline, ring back on your mobile. I'm not sure if it's always the case, but I believe that a call to a landline only terminates when the caller hangs up. This certainly used to be the case. This allows scammers to ask you to hang up and call them back on the number on your card (for example), but they just mimic the dial-tone and ring, then they have another scammer answer the phone. Thi…

I haven't seen a landline in ages...

They are buried.

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

#97

Post by sschueller »

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 provider has his own number prefix. Numbers are portable but only between certain providers.

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

#98

Post by drcongo »

deadcore wrote: post #28

The how - depending on the protocol. Signalling System No. 7 - ISDN User Part spec (found here: https://www.itu.int/rec/T-REC-Q.763-199912-I/en ) allows you to specify both a calling party number (3.10) and generic number (3.26) (the UK spec adds an additional presentation number so you have 3). This will typically require the help of an operator which is 'connected' to the network on the PSTN. A real business case c…

Does that addition in the UK spec add any extra protection? I've never had a spam call with a spoofed number in the UK as far as I'm aware, and definitely never seen that thing that happens in the states where a call comes in showing the name or company name of the caller, even if they're not in the receiver's address book.

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

#100

Post by arcticbull »

Used to take about 5 minutes to configure an Asterisk [1] PBX, obtain a provisioned DID from a VoIP provider and set your outbound caller ID with Set(CALLERID()) [2]. Doing so allows you to configure both your text label and call-back number.

[1] https://www.asterisk.org/

[2] https://www.voip-info.org/setting-callerid/

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