Spoofing just changes the displayed called/sender ID, not the actual number. They would still need real numbers for each account. And they block a lot of VoIP numbers, like most services these days. And getting carrier SIMs or e-SIMs is a not that easy.
Isn’t spoofing a phone number easy for scammers? If so, I don’t understand why there is (admittedly) so little spam on Signal.
Does Signal require 2FA upon registration? (I cannot recall)
Spoofing just changes the displayed called/sender ID, not the actual number. They would still need real numbers for each account. And they block a lot of VoIP numbers, like most services these days. And getting carrier SIMs or e-SIMs is a not that easy.
No mandatory 2FA as far as I know.
Then how is the authenticity of a number tested by Signal?