I've never knowingly provided my cell number to facebook, as I don't use facebook as an o-auth provider so I consider 2fa as less important that my privacy in this case.
I'm a product even without having signed up.
EDIT: Shouldn't I have some kind of say in that?
'Shadow profiling' ought to be 100% illegal.
They have no business propagating that information any further than the profile that supplied it.
They can read your number there.
I'm fairly accepting that every android app asks for "permission to read ..." permissions, but I don't want them to be so proud of this that they present their information back to me.
That's what is so creepy about Facebook, they've lost sense of what is normal, so they don't hesitate to show off how much they know.
I'm sure Google knows a lot more about me, but they have the sense not to parade that fact back to me unless I specifically ask.
Same with LinkedIn, who installs this crap? And why?
Of course, there's plenty of other crap on my phone that I've installed and is exposing me...
For me Facebook is a necessary evil. I'm not willing to miss the family trips that only get planned there so I just attempt to minimize damage.
Maybe what's normal has changed out from under you.
and the number can also come from a friend phonebook within one of the aforementioned apps
The permissions include:
Device ID & call information read phone status and identity
From: https://support.google.com/googleplay/answer/6014972?hl=en Device ID & call information
An app can access your device ID(s), phone number, whether you're on the phone, and the number connected by a call. Device ID & call information may include the ability to read phone status and identity.
Which returns "null" unless the operator actually stores the phone number in the SIM so it can be read from there (also it can be modified to be anything). While technically possible, I have not seen it in practice for long time (since 2010 or so).
On iPhone it's not possible for an application to obtain the phone number[2]. There was a semi-hack doing so and Apple rejected the applications off the store and closed the loop. (reading SBFormattedPhoneNumber)[3]. In 2013 there was another exploit to obtain it but it has been addressed as well.
[1]: http://developer.android.com/reference/android/telephony/Tel... [2]: https://www.google.com/?gws_rd=cr,ssl&ei=GNa4Vc3ODuxxxxrQCg#... --it's google search with the reject terms [3]: https://www.cocoanetics.com/2009/11/forbidden-fruit-apple-ap...
Personally I have not seen an EU provider storing a real phone number there.