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Comment by maym86 | Hacker News Reader

How does it work? Why is it so easy?

Well there's a few issues.

The SS7 (https://en.wikipedia.org/wiki/Signalling_System_No._7) does not have any authentication so anything over the telephone networks can be easily MITM'd.

And at provider's stores they are too eager to please a "customer" so social engineering is very effective at swapping SIM cards out and hijacking your number.

It's easy because a) the signaling system in use is pathetically insecure, b) the wireless protocols are pathetically insecure.

SMS is not exactly the most secure protocol. But you do not need to use SMS for 2fa, that's a misconception.

Isn't it effectively plaintext?

I don't know too much about the SMS protocol. But I do know that most protocols do start out plaintext because programmers are lazy and optimistic.

That’s one part of the problem. The other part is that it’s actually quite easy to convince most cell phone carriers to change the SIM card associated with a given phone number. Once you’ve pulled that off hijacking the account is easy.

It's not exactly plaintext. Last time I saw it was using broken crypto (may have changed since then, but I doubt it), and it encrypts the data hop by hop, so that if you insert yourself as a hop, you'll just have decrypt (with your keys), read and encrypt it.

Search for SS7, it's a swiss cheese of vulnerabilities.

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