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When logging in to Facebook/Yahoo mail, I receive my 2FA codes from random numbers. Here are some examples (I have a Romanian phone number, hence the country codes):

+40 747 691 103
+40 727 347 814
+40 758 942 742
+40 759 158 056

and the list goes on. It's a different number every time.

Furthermore, the text in the messages that I receive is grammatically all over the place. Looks like a legit spam SMS. However, the codes inside do work! I find this immensely odd.

Considering potential malware somewhere, I tried formatting my drive and reinstalling the OS. I also did a factory reset on my smartphone and the result is still the same. I even got a new SIM card and a new phone.

What I would expect is not to see a particular phone number, but only "Facebook" or "Yahoo" as the sender of the SMS. Could there be a man-in-the-middle?

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  • You should ask Facebook and Yahoo why they use particular telephone numbers. This question is out of scope of Security SE site. I suggest to close this question.
    – mentallurg
    Commented Mar 11, 2021 at 19:07
  • I apologise, I do not mean to ask out-of-scope questions. However, first, I have seen similar questions around. Second, one might indeed suspect an attack. Does that not make this community relevant?
    – hyperio
    Commented Mar 12, 2021 at 8:38
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    This is lacking a bunch of information and context and it is very confusing. Of particular interest is "the codes inside do work". You mean that when you log in and are prompted for 2FA, you receive a valid code, but from unexpected numbers?
    – schroeder
    Commented Mar 12, 2021 at 9:43
  • Yes, that is what I mean. Sorry about the confusion.
    – hyperio
    Commented Mar 12, 2021 at 10:07
  • We have had a few questions just like this over the years. No, it's not an attack. It's a way for the company to avoid SMS charges. Spoofed numbers and invalid formatting/spelling/etc. to avoid detection from SMS providers...
    – schroeder
    Commented Mar 12, 2021 at 20:50

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