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Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner

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On 2026-06-10 21:29, VanguardLH wrote:
> "Carlos E.R." <robin_listas@es.invalid> wrote:
> 
>> This is an article in Spanish, translated. I do not know if it applies
>> worldwide.
>>
>> <https://bandaancha.eu/articulos/android-detectara-llamadas-numero-falso-11792>
>>
>> Android will detect calls with spoofed numbers by sending a real-time
>> RCS message to the legitimate owner
>>
>> By Joshua Llorach
>> Published 3 June 2026 10:50
>>
>> Until last summer, it was very easy for malicious actors to spoof the
>> number that appears on a mobile phone screen as the caller ID when a
>> call rings. The lack of a system to validate numbers and their origin
>> allowed spammers and other malicious actors to inject traffic into the
>> network with a spoofed caller ID, a practice known as CLI spoofing.
>>
>> Since June 2025, mobile operators have been filtering calls originating
>> from abroad that use Spanish numbers without permission, as well as
>> applying other validation checks to make this practice more difficult.
>> Added to these measures is the system from Orange and Telefónica that
>> displays a warning on the screen for suspicious calls.
>>
>> Falsifying a number known to the victim makes the attack much more
>> effective, especially in the age of AI, where it is very easy to imitate
>> a person’s voice, so Google is joining this fight with its own measures
>> against CLI spoofing.
>>
>> The Android Phone app has started to verify the caller ID of incoming
>> calls by connecting in real time to the supposed originating mobile
>> phone to check that it is indeed the one making the call.
>>
>> For this to work, both parties must be Android users with the Phone app.
>> When the call rings on the recipient’s device, the phone sends an
>> encrypted RCS message to the legitimate owner of the number to ask if
>> they are actually making the call at that moment. In this way, the
>> recipient’s phone can tell when the call is fake.
>>
>> The idea is interesting, as it does not use OTT data traffic, but rather
>> core network services, making the exchange of information faster and
>> more reliable.
>>
>> This feature is being rolled out first on Pixel devices running Android
>> 12 and above, but Google has released it as an open standard so that
>> other phone apps and operating systems can use it, meaning that in the
>> future it would be possible to verify numbers between Android and iOS if
>> the parties involved wish to do so.
>>
>> Translated with DeepL.com (free version)
> 
> So the non-spoofed caller makes their call, and then has to respond to a
> text message?  Oh joy, 2FA comes to voice calls, too.

Yes, I wonder.

> 
> "When the call rings on the recipient’s device, the phone sends an
> encrypted RCS message to the legitimate owner of the number to ask if
> they are actually making the call at that moment."
> 
> One, only works when caller and callee are both Android users, and both
> use a phone app with the integrated verification check. 

The Google telephone app, which is the default.

> Two, to
> eliminate 2FA interference, the caller's phone app must automatically
> respond to the RCS request by the callee's phone app, and the callee's
> phone app must automatically handle the RCS response.
> 
> Texting is not a guaranteed communication venue.  What happens when a
> call is received, but texting fails in either direction between caller
> and callee?  And how does this scheme eliminate the delay in getting the
> specially encoded text?  Texting is not always immediate.  Who is going
> to wait 2 minutes for the texting to complete in both directions when
> there is an incoming call?  After how many rings should the callee wait
> before picking up the call?  Will the callee's phone app silence all
> ringing until its validation text gets received by the caller, and the
> caller's phone app sends back the response text, to when the callee's
> phone app finally gets that response text?
> 
> I'm sure there are some glitches that will have to get ironed out.
> Since texts are an insecure communication venue (no encryption), 

It is RCS, there is encryption.

> there
> wouldn't be some means to spoof the response text the spammer sends to
> the callee?  There are entire companies dedicated to providing spoofing
> services, so I'm sure they'll figure out a workaround.


-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

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Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E.R." <robin_listas@es.invalid> - 2026-06-10 11:44 +0200
  Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Jörg Lorenz <hugybear@gmx.net> - 2026-06-10 17:59 +0200
  Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-10 14:29 -0500
    Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E.R." <robin_listas@es.invalid> - 2026-06-10 23:19 +0200
    Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Theo <theom+news@chiark.greenend.org.uk> - 2026-06-11 22:32 +0100
      Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-11 20:18 -0500
        Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E.R." <robin_listas@es.invalid> - 2026-06-12 12:16 +0200
          Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-12 15:13 -0500
            Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Andy Burns <usenet@andyburns.uk> - 2026-06-13 08:29 +0100
              Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-13 15:52 -0500
                Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Jörg Lorenz <hugybear@gmx.net> - 2026-06-14 07:35 +0200
      Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Jörg Lorenz <hugybear@gmx.net> - 2026-06-12 07:19 +0200
      Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E.R." <robin_listas@es.invalid> - 2026-06-12 12:19 +0200
        Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-12 15:59 -0500
      Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Theo <theom+news@chiark.greenend.org.uk> - 2026-06-12 23:11 +0100
        Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E. R." <robin_listas@es.invalid> - 2026-06-14 15:05 +0200
          Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-14 20:18 -0500
            Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E. R." <robin_listas@es.invalid> - 2026-06-15 09:24 +0200
              Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner VanguardLH <V@nguard.LH> - 2026-06-15 08:14 -0500
                Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner Theo <theom+news@chiark.greenend.org.uk> - 2026-06-15 16:29 +0100
                Re: Android will detect calls with spoofed numbers by sending a real-time RCS message to the legitimate owner "Carlos E. R." <robin_listas@es.invalid> - 2026-06-15 21:21 +0200

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