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FWIW I wouldn't regard SMS as a good 2nd authentication factor either, for the same reasons as this issue, it's too easy to get a carrier to transfer a number t
by raesene9 5y ago
FWIW I wouldn't regard SMS as a good 2nd authentication factor either, for the same reasons as this issue, it's too easy to get a carrier to transfer a number to an attacker.
Where it's used as a second factor, this still has an impact which is, if an attacker can get the password (and there's been enough breaches and keystroke logging for that to be common) they can then grab the number to get full control of the account.
TOTP or hardware tokens don't generally suffer from the same problem.
- addingnumbers 5y agoThe problem is with most online services, the only second factor allowed is SMS. If you see it as "don't bother, they can just steal your SMS number" instead of "that's slightly better, at least now they can't get in without stealing my number" then you're not thinking about this reasonably. It's inane to neglect to use SMS where it's the only second factor available. The exception is when a service allows you to use SMS alone for password resets, which isn't MFA, is 1FA with a weaker factor than a password. What would you think if someone took you for a joyride in a classic car and said "shoulder belts would be so much better than these lap-only belts, so don't bother buckling up!"
- raesene9 5y agoI didn't say it was worse than just password, I said it was a bad second factor, which it is. SMS 2FA was vaguely reasonable before TOTP applications and smartphones capable of running them were widely available. That's no longer the case.
- iso1210 5y agoWhat's the recovery process when your phone gets stolen, or you drop it?
- raesene9 5y agoFor me, for TOTP, I use one that backs up to iCloud. that obviously weakens the security, but increases the availability. With some applications, you can add additional devices, so you can add multiple, if you have 'em.
- addingnumbers 5y agoA bad second factor is better than no second factor. I enabled TOTP on every account I have that supports it, which comes to about 2 out of every 5 services. I'm not going to leave the other 60% with only one factor just because SMS can be exploited, which the consensus in this thread seems to be advising everyone to do.
- profsnuggles 5y agoIf someone can exploit your SMS, it's possible they can use that to social engineer their way into a password resets with services. (I forgot may password but I still have my phone.) So I would say a bad second factor can be strictly worse than no second factor.
- addingnumbers 5y agoYou're describing single factor, not two factor. If you can change the password with SMS alone, it's not multi-factor. I plainly stated that exception two comments ago.
- profsnuggles 5y agoExcept you have no way of knowing if that will be the case ahead of time. Unless the first thing you do after enabling 2FA is to social engineer a password reset for your account? Even then that doesn't guarantee that there isn't a more clueless service rep that will make a mistake. Asking before you sign up, "will you allow my account to be hacked through social engineering?" isn't going to an answer other than no. Even if the answer is possibly yes.
- FabHK 5y agoBut then let's please move the discussion from "Is SMS a good or bad second factor?" to "SMS is a mediocre second factor, and a terrible single factor. For this service, is it a second or single factor?"
- jjav 5y ago
- VRay 5y agoBasically every service I've used that requires SMS will use it as the sole authentication factor for resetting your password.. It's brutal
- realusername 5y agoSMS is the only "second factor" that you can't control at all, your phone number can be changed from the phone company at any point, disabled, or suddenly refuse to work in a foreign country (all of those three happened to me). For those reasons, even as a second factor it's a terrible one. SMS is just not a good method of authentication at all and has no place in a login form. At it's best, SMS is only useful as a read-only notification system for non-sensitive purpose.
- UncleMeat 5y agoTOTP is phishable, which is a way way way more common attack than sim swaps.
- 2rsf 5y agophishable how? "your account has been hacked, please provide us a TOTP code"?
- UncleMeat 5y ago1. Somebody loads fakebank.com. 2. It pops up a username/password screen. The user types in their credentials for realbank.com. 3a. The owners of fakebank.com use your creds to log in to realbank.com and are presented with a TOTP page. 3b. fakebank.com loads another page that asks the user for their TOTP. The user enters it, still thinking they are logging in to realbank.com 4. The owners of fakebank.com use the TOTP to authenticate as the user with realbank.com. Entire SDKs to automate this are sold on the black market.
- sgerenser 5y agoCouldn’t this entire scenario play out exactly the same with SMS codes?
- UncleMeat 5y agoYes. The point is the TOTP is precisely as bad as SMS for the common case (phishing) and only safer in a rare case (SIM-swap). This comes with large downsides (losing access). TOTP is, at best, a very marginal improvement over SMS. This is what makes the online push to complain about services that use SMS 2FA and demand a switch to TOTP very strange.
- dheera 5y agoTOTP is far, far better for travellers who need to swap their SIM cards frequently, or need to work out of places with internet access but no cell reception.
- mrweasel 5y ago> TOTP or hardware tokens don't generally suffer from the same problem. But how many hardware tokens or TOTP tokens are users willing to deal with? I currently have eight for various clients and systems at work. If each online account required a TOTP token or a custom hardware token it would be a confusing mess of tokens. I don't know if there's a safe and easy way of reusing the same token across sites. Until then SMS really is the only "solution".
- PeterisP 5y agoIt is safe to use the same U2F token for many sites, that's not an issue. Having a backup token is very useful, but apart from that, a single hardware token (not custom - standards are good) can easily be used to secure all your accounts.
- mrweasel 5y agoAssuming that the sites allow you to change the token manually?
- tialaramex 5y agoI've never seen a site that didn't have at least this. Usually you get a UI where you can add new ones and remove old ones, and when you add a new one you name it in their UI so that you can tell it apart from any others.
- dheera 5y agoThe only thing I wish is that more sites support multiple tokens, since tokens can get lost. If you only support one token but have an easy recovery procedure, that opens up loopholes. If you support multiple tokens, allow the user to de-activate one token from another token, and make recovery difficult, that's much more secure.
- tialaramex 5y agoAgain, other than AWS which "more sites"? Dropbox, Facebook, Google, GitHub, GitLab, even Login.gov works fine with multiple tokens. More sites should do WebAuthn (you should not do greenfield deployments of U2F today, WebAuthn is the standard). Yes, AWS should fix their feature but that shouldn't block the next ten would-be Unicorns from doing WebAuthn.