Scam calls from foreign numbers that appear as domestic
October 13, 2019 12:48 AM Subscribe
How does one caller ID system show me a different number for the same caller. One has +1 (appearing as a US Domestic call), the other does not (appearing as International).
I'm asking this mostly because I want to understand the technology at work here. I have been getting slightly upsetting but obvious scam calls from foreign numbers (the sort asking for personal information or else threats). The person on the other end of the line is typically real with a strong accent.
What is strange though is that the calls come through as international (I have AT&T), but the voicemails come through as domestic. To give an example, I will get a call from Europe or North Africa, using a +4 or +2 number, but then if I do not answer I will get a voicemail from the SAME or similar number appended with +1.
For instance, I will get a call showing up as +44 2XX-XXX XX but the voicemail record will show as + 1 (442) XXX-XXXX. Is this some CDMA/GSM thing?
Again, I realize this is a scam and probably nothing to worry about. I also realize telephone numbers are easily spoofable and not secure. What I want to understand is how this could happen from a technical perspective. In the voicemails the scammers are typically telling me to call them at the domestic line, not the international line, so are they somehow in control of both numbers?
How is it that my caller ID says one thing and my voicemail adds a +1 ?
Thanks!
I'm asking this mostly because I want to understand the technology at work here. I have been getting slightly upsetting but obvious scam calls from foreign numbers (the sort asking for personal information or else threats). The person on the other end of the line is typically real with a strong accent.
What is strange though is that the calls come through as international (I have AT&T), but the voicemails come through as domestic. To give an example, I will get a call from Europe or North Africa, using a +4 or +2 number, but then if I do not answer I will get a voicemail from the SAME or similar number appended with +1.
For instance, I will get a call showing up as +44 2XX-XXX XX but the voicemail record will show as + 1 (442) XXX-XXXX. Is this some CDMA/GSM thing?
Again, I realize this is a scam and probably nothing to worry about. I also realize telephone numbers are easily spoofable and not secure. What I want to understand is how this could happen from a technical perspective. In the voicemails the scammers are typically telling me to call them at the domestic line, not the international line, so are they somehow in control of both numbers?
How is it that my caller ID says one thing and my voicemail adds a +1 ?
Thanks!
As flabdablet says, the number being displayed is the number that the caller *claims* they're calling from--these are very easy to spoof, such that they're completely divorced from having control over the number. Since these are high-volume scams, these could also be screw-ups.
My guess is that, if it's not trying to spoof a number designed to impress the caller, that the "international" number is a mis-formatting of the throwaway domestic number they want you to call back.
posted by pykrete jungle at 7:21 AM on October 13, 2019
My guess is that, if it's not trying to spoof a number designed to impress the caller, that the "international" number is a mis-formatting of the throwaway domestic number they want you to call back.
posted by pykrete jungle at 7:21 AM on October 13, 2019
This thread is closed to new comments.
+44 is the international prefix for the UK, but 2XX-XXX XX is only eight digits and any genuine UK number starting with 2X would have ten. So your voicemail system has a choice of which formatting error to "fix", and it's chosen to insert the "missing" 1 to make the number it's been given into one whose format fits a genuine US pattern.
The number that shows up on your handset's caller ID is probably exactly what the caller is sending, regardless of whether that's valid or not. Here in Australia I get scam calls with visibly bogus numbers pretty much daily. High-volume phone scamming is shotgun, not scalpel.
posted by flabdablet at 5:02 AM on October 13, 2019 [2 favorites]