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    An interesting aspect of this: their employees’ credentials were compromised by intercepting two-factor authentication that used SMS. Security folks have been complaining about SMS-based 2FA for a while, but it’s still a common configuration on big cloud providers.

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      What’s especially bugging me is platforms like twitter that do provide alternatives to SMS for 2FA, but still require SMS to be enabled even if you want to use safer means. The moment you remove your phone number from twitter, all of 2FA is disabled.

      The problem is that if SMS is an option, that’s going to be what an attacker uses. It doesn’t matter that I myself always use a Yubikey.

      But the worst are services that also use that 2FA phone number they got for password recovery. Forgot your password? No problem. Just type the code we just sent you via SMS.

      This effectively reduces the strength of your overall account security to the ability of your phone company to resist social engineering. Your phone company who has trained their call center agents to handle „customer“ requests as quickly and efficiently as possible.

      update: I just noticed that twitter has fixed this and you can now disable SMS while keeping TOTP and U2F enabled.

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        But the worst are services that also use that 2FA phone number they got for password recovery. Forgot your password? No problem. Just type the code we just sent you via SMS.

        I get why they do this from a convenience perspective, but it bugs me to call the result 2FA. If you can change the password through the SMS recovery method, password and SMS aren’t two separate authentication factors, it’s just 1FA!

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          Have sites been keeping SMS given the cost of supporting locked out users? Lost phones are a frequent occurrence. I wonder if sites have thought about implementing really slow, but automated recovery processes to avoid this issue. Going through support with Google after losing your phone is painful, but smaller sites don’t have a support staff at all, so they are likely to keep allowing SMS since your mobile phone number is pretty recoverable.

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            In case of many accounts that are now de-facto protected by nothing but a single easily hackable SMS I’d much rather lose access to it than risk somebody else getting access.

            If there was a way to tell these services and my phone company that I absolutely never want to recover my account, I would do that in a heartbeat

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            This effectively reduces the strength of your overall account security to the ability of your phone company to resist social engineering. Your phone company who has trained their call center agents to handle „customer“ requests as quickly and efficiently as possible.

            True. Also, if you have the target’s phone number, you can skip the social engineering, and go directly for SS7 hacks.

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            I don’t remember the details but there is a specific carrier (tmobile I think?) that is extremely susceptible to SMS interception and its people on their network that have been getting targeted for attacks like this.

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              Your mobile phone number can relatively easily be stolen (more specifically: ported out to another network by an attacker). This happened to me on T-Mobile, but I believe it is possible on other networks too. In my case my phone number was used to setup Zelle and transfer money out of my bank account.

              This article actually provides more detail on the method attackers have used to port your number: https://motherboard.vice.com/en_us/article/vbqax3/hackers-sim-swapping-steal-phone-numbers-instagram-bitcoin

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                T-Mobile sent a text message blast to all customers many months ago urging users to setup a security code on their account to prevent this. Did you do it?

                Feb 1, 2018: “T-Mobile Alert: We have identified an industry-wide phone number port out scam and encourage you to add account security. Learn more: t-mo.co/secure”

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                  Yeah I did after recovering my number. Sadly this action was taken in response to myself and others having been attacked already :)