SMS

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SMS, t(e)xt messaging, or t(e)xting is a highly insecure way to send short text messages to or from a cell phone, also often used as a second factor for TFA, or worse, password reset (has resulted in account hijackings), and is misguidedly encouraged for such in iOS version 10+, Twitter, Facebook, and other software or services that nag you to associate an SMS phone number with your account on their systems.

MMS is used for sending media such as photos in otherwise "text" messages.

Criticism

Insecure Account Recovery

Insecure Second Auth Factor

  • 2018-08-01 We had a security incident. Here's what you need to know.
    • "Already having our primary access points for code and infrastructure behind strong authentication requiring two factor authentication (2FA), we learned that SMS-based authentication is not nearly as secure as we would hope, and the main attack was via SMS intercept. We point this out to encourage everyone here to move to token-based 2FA."
  • 2018-07-17 Motherboard: The SIM Hijackers
    By hijacking Rachel’s phone number, the hackers were able to seize not only Rachel’s Instagram, but her Amazon, Ebay, Paypal, Netflix, and Hulu accounts too. None of the security measures Rachel took to secure some of those accounts, including two-factor authentication, mattered once the hackers took control of her phone number.
    Emphasis added.

Silo Examples

(need screenshots from the nag-ware screens from Apple (iOS 9+ nags you on first start, iOS 10+ nags you continuously in Settings app), Google, Facebook etc encouraging/defaulting you to add your cell phone number for auth / recovery reasons).

Also need screenshots from any services that when you add SMS as a second factor, they default to adding SMS as an account recovery method (1-factor), which actually makes your account *LESS SECURE* than if you would have never attempted to turn on 2FA in the first place.

Apple ID

Apple ID is a silo identity service that is now (all but?) required to use any iOS or MacOS device.

On MacOS, you are prompted by the "Settings" app to associate a phone number that can receive SMS with your Apple ID to "verify your identity":

2017-02-17-macos-2fa-sms-settings-e.png


Instagram

Instagram only allows SMS based MFA and then enables SMS recovery as well thus making your account MORE vulnerable (e.g. to SIM-jacking as documented) than if you had never turned on their MFA.

  • 2018-07-17 Motherboard: The SIM Hijackers
    Certain services, including Instagram, require that users provide a phone number when setting up two-factor, a stipulation with the unintended effect of giving hackers another method of getting into an account. That’s because if hackers take over a target’s number, they can skirt two-factor and seize their Instagram account without even knowing the account’s password.


Twitter

Twitter actually prompts you to add a phone number to your account (if you don't already have one on it) with SMS password reset *as a feature*! They are literally prompting you to make your account *less* secure, while claiming the opposite. WTF.

2017-09-27-twitter-add-sms-pw-reset-prompt.png

Text of prompt reads (emphasis added):

Safeguard your account

Add your phone number now to help ensure that you can log in to Twitter, even if you lose your password


What the prompt really means:

Make your account vulnerable

Add your phone number now to help ensure that anyone pretending to be you to your phone company can log in to Twitter, even without your password

See Also