7 ms·

You don’t need SMS-2FA

• jasonpeacock 6y ago
  He's arguing not just against SMS-2FA, but against 2FA itself, and his simple solution is to "just use a strong password". The author completely misses the point about the value of 2FA itself. I agree SMS-2FA is not good, but that doesn't mean 2FA is worthless.
  • UncleMeat 6y ago
    Sort of. He discusses the benefits of phishing resistant approaches like u2f later in the article.
  • pkulak 6y ago
    I guess he was trying to specify 2FA that's NOT u2f, or other very strong options. But yeah, in principal, he's really talking about SMS, TOTP, et all. Bit of a shame, because TOTP itself is far better than SMS. It's all a sliding scale of security vs convenience.
    • packet_nerd 6y ago
      Except it's not really a sliding scale with SMS being "easy" and U2F being "hard". U2F is SO much more convenient than either TOTP or SMS. SMS might be a little easier than TOTP, but with either one you still have to (1) find the phone, (2) unlock it, (3) hunt around for and open the app, (4) manually type the code in, often looking back and forth between the phone and webpage 2 or more times before you get it. Compare to just taping the U2F key with the side of your finger (assuming it's already plugged in, which is what I do). There's just no comparison in terms of UX between U2F and anything else I've ever seen.
      • pkulak 6y ago
        Can you use the same USB key for every application you need to authenticate to?
        • tialaramex 6y ago
          Web sites can all just do WebAuthn. The browser will securely manage the relationship between each site and the USB key ensuring that sites can't lie to the key about who they are (which would enable phishing). If you are happy to use this only as a second factor, the USB key can handle any number of sites without constraint. If you want "resident credentials" where the USB key can sign you in spontaneously (no need to even enter a username or email address) the key needs storage for each such credential, those on the market today hold only a relatively small number, fine for your bank but not for say Hacker News and other forum sites you might join dozens of. For other application software it's trickier but possible, you can see that OpenSSH did this for example.
        • packet_nerd 6y ago
          Yes (If the service supports U2F)
    • jsnell 6y ago
      There are security dimensions on which TOTP is worse. It's plausible for the SMS code to contain enough information about the login attempt to make the user realize they're being phished. "Are you trying to log in from Ukraine? If yes, the code is 123456." "Bank tranfer of 10000 EUR to account XYZ: verification code 987654" TOTP obviously can't do this.
• hprotagonist 6y ago
  SMS 2-factor is wrong and bad and NIST has been yelling about this since 2016 or before. Simjacking is real and fairly commonly used in targeted attacks. 2-factor as an idea is great, and this author seems very confused.
  • jandrese 6y ago
    SMS should only ever be used as a proof of investment. IE making sure a bit setting up hundreds of thousands of accounts (because they broke your CAPCHA) needs to buy tens of thousands of real phone numbers with service. It’s a one time thing at account creation and should be immediately deleted afterwards. Real 2FA should be set up afterwards to actually protect the account. A yubikey or even a simple TOTP app is a lot of protection against account takeover. The only big weakness left at that point is the help desk.
    • UncleMeat 6y ago
      > TOTP app This is only very marginally more effective than SMS. Phishing is way more common and can be automated much more easily than SIM-swapping. With TOTP you close a small window but leave the big door open. Yubikeys prevent phishing, which is enormously valuable.
    • frei 6y ago
      All the arguments in the post against SMS 2FA are also arguments against TOTP
      • jandrese 6y ago
        There is no help desk that can give away your TOTP secret. That’s the big weakness with SMS, someone buys a phone and asks the clerk to give them your phone number.
        • UncleMeat 6y ago
          It is a publicized weakness. In practice, phishing is scalable and social engineering isn’t. And humans are shit at detecting phishing attacks.
• lostmsu 6y ago
  I did not get the explanation for why SMS 2FA does not work against credential stuffing. It clearly does.
  • UncleMeat 6y ago
    He is thinking of it from the user’s perspective rather than the service. If I reuse my passwords I still get owned even if some of my services use 2fa, because others won’t. It’s an unusual way of thinking about it and I think the weakest part of his argument but it is interesting.
    • lostmsu 6y ago
      Yeah, that basically destroys his argument. If I use the same password for a random internet forum with no 2FA and my bank account with SMS 2FA, then a person, who breaks into the forum DB still can not access my money.
      • ozim 6y ago
        Problem is that attackers can take advantage of that random internet forum to take over your bank account. Plant something that you would click because it is on your account and it downloads some malware. Could come up with more scenarios probably like they could target someone else from your account and use trust you have on that forum. But it is of course question if you are worth their time.
        • lostmsu 6y ago
          What you said has nothing to do with SMS 2FA, and has everything to do with user/their friends' gullibility, which still must be pretty high to click something on the forum and then also launch it. It also is totally unrelated to credential stuffing. We are not looking for a panacea there. If you're that gullible and your forum account is pwned, no security measures will prevent you from giving up bank details.
  • 33Backpack33 6y ago
• scott_s 6y ago
  I believe the arguments that SMS-2FA is not effective against phishing. (Or, at the least, I can't provide a compelling counter-argument.) But I had always thought of SMS-2FA against a more banal problem: 1. You have a unique, long password with Foo. 2. Oh no! They store your password in plaintext, and their security is terrible, so your username and password are part of a giant data breach from Foo. 3. Before you know about it and can change your password, someone that is not you, who does not have access to your phone, tries to log into the account. 4. While out living your life (or in, these days), you receive an SMS from Foo, and then ignore it. 5. There is no step 5, as no one else is getting in. 6. Okay, fine, you caught on, and now you log in and change your password with Foo, or maybe just drop the account, because really. It seems to me that SMS-2FA helps in this scenario. Am I missing something obvious?
  • UncleMeat 6y ago
    Tavis discusses this explicitly in the article. His claim is that there will be some other service that doesn’t do this so the user is still vulnerable to credential stuffing - just not on your service. I don’t fully buy the argument, but he didn’t just ignore this. More valuable, I think, is the claim that we only get so much bandwidth to educate users and that spending time educating people on unique passwords is more effective than working on sms 2fa.
    • toomuchtodo 6y ago
      Users are lazy. You can educate all you want, they will still use the same passwords everywhere, or weak passwords. You have to bake the security into your workflows, processes, and code if you want it to matter. This is from infosec/opsec awareness training experience I get paid to provide. Not all users are lazy, mind you, but enough to be emotionally depleting. Incentives matter.
      • UncleMeat 6y ago
        > You have to bake the security into your workflows, processes, and code if you want it to matter. There's a suggestion here in the article: don't let users pick their passwords. Just generate one for them and say "use your browser's password manager or write it down".
• solvorn 6y ago
  “Why wear a seatbelt your car can crash and you can die anyway.”
• wyc 6y ago
  Yes, it's true that SMS-based authentication has its flaws, but it's far from useless/harmful in many contexts. The same strawman arguments used here would also find TOTP "wholly ineffective" which is an absurd conclusion. A main goal of security engineering is to increase the difficulty level for attackers. SMS authentication has demonstrated its ability to do this in a highly accessible, albeit imperfect, manner. I feel that the author severely underestimates the practical difficulties of widely deploying "Unique Passwords and U2F". I strongly disagree with the conclusion that "SMS-2FA is not only worthless, but harmful" and highly recommend consulting a security professional before entertaining any of the arguments or following any of the suggestions in this article. I don't like leaving negative comments, but this is at best borderline misinformation that has the potential to create severe consequences. Some more context, if you want to consider a more balanced perspective: https://doublepulsar.com/infosecs-fantastic-fear-of-everything-why-the-reddit-incident-shouldn-t-cause-infosec-to-throw-4bb3b7ea634f https://doublepulsar.com/infosecs-fantastic-fear-of-everythi...
  • exabrial 6y ago
    I would argues SMS is worse than "nothing at all", as it moves the responsibility [unwillingly|unknowingly] to the person's carrier, who likely [demonstratively] are not hardened against attack.
  • packet_nerd 6y ago
    Regarding the "SMS-2FA is not only worthless, but harmful" claim, it's true, but only in the sense that widespread "lazy" SMS 2FA deployments stifle U2F, which, I believe, should just be the standard across the board[1]. Of course SMS does help, just not as much or in as many attack scenarios (and is more of a UX pain too). [1] The common HN objection which you alluded to is "but it's so hard!" It's really not. Passwords are hard! If only I could have back all the hours I've spent trying to help my grandparents remember their passwords. I have a U2F token plugged into the side of laptop and nothing could be easier than tapping it to get in. Implementation might be hard, but come on, that's our job.
  • jolux 6y ago
    Tavis Ormandy is definitely a security professional, he works for Project Zero.
• exabrial 6y ago
  SMS 2FA exposes a person's cell phone account to attack, and the carriers aren't hardened to handle it. Jack Dorsey getting hacked proves how stupid using SMS for anything. Please, implementing this. Use FIDO U2F or TOTP. It's not that hard, my 70 year old mother has it enabled and has no issues with it.
• freeone3000 6y ago
  Okay, the argument about credential stuffing is fairly weak. 2FA on a given service makes it an ineffective attack against that service. If you have 2FA on all of your services, credential stuffing won't work on any of them, so you're then immume. Moreover, not all services are identical - Email merits two distinct hardware keys, my Steam account warrants an emailed password, my BeerAdvocate account... probably doesn't need anything.
• deleted 6y ago
  [deleted]
• jsnell 6y ago
  > Unfortunately, it doesn’t work like that. When a service enables SMS-2FA, an attacker can simply move to a different service. That argument is just nonsensical. If you're a provider, the user being compromised on some other service doesn't really matter (and there's nothing you can do to prevent it anyway). While preventing the compromise protects the platform from abuse, saves on customer support on having to help the hijacked user recover, etc. While if you're a user, obviously it's better to be hijacked on as few (and as unimportant) services as possible. > Instead, why not simply randomly generate a good password for them, and instruct them to write it down or save it in their web browser? The users don't know how to save a password in the web browser. They'll lose the piece of paper. They'll be unable to log in, and effectively end up in an eternal loop of recovering their account (with SMS!) every time they log in, and getting a new password they can't remember. If you end up sending the user an SMS anyway on every log in, might as well use the version where you get to use knowledge of the password as a gating factor. > If we spend all that good will on irritating attackers, then by the time we’re ready to actually implement a solution, developers are not going to be interested. I'm really not sure what this is referring to. Other than this comment, I thought Tavis was railing against forcing users to do SMS 2FA. But then it turned out that the resource he is concerned about is developer goodwill, which doesn't really make sense. There are a few classes of developers. 1. Huge companies with security teams that are willing to entirely implement their own authentication systems. Their goodwill is not going to be exhausted, since they're implementing what those teams think is the best for their platform's security. 2. Companies with potentially sensitive data who outsource some or all of the authentication to some kind of identity provider or identity platform. Their goodwill won't be exhausted: they'll just expect the provider to implement whatever the best practice is at any time. 3. Companies that don't care, and just roll their own username + password auth. They aren't going to implement SMS 2FA any more than they would implement U2F.
  • shawkinaw 6y ago
    > > Unfortunately, it doesn’t work like that. When a service enables SMS-2FA, an attacker can simply move to a different service. Yeah I really don't understand their argument here, to the point that I feel like I must be missing something.
  • 6y ago
• zachrip 6y ago
  The thing I find odd about sms 2fa is I sometimes get multiple services texting me through the same short code. Isn't that a security hole in itself? If a user recognizes a number as the "security number that texts me sometimes" and I as an attacker know this, couldn't I somehow abuse this? For example: "Please go to x url and enter your password" -> user enters pw -> show new form with 2fa code input (and in the background, try logging into their account with the pw supplied) -> user gets another text from the same number, enters in your site -> profit???
• 7786655 6y ago
  After multiple experiences where I couldn't log into an account due to not having a phone signal, I refuse to use SMS-2FA on any service. Given that I already use strong passwords, the marginal security advantages are far outweighed by the potential lack of availability.
• thoraway1010 6y ago
  I've got the dual yubico key thing going. It seems to work fine. I don't need to pick overly complex passwords if I don't want to. Google does this well. Yubico Security Key + they seem to monitor my logins / rate limits etc. I deal as do many folks with relatively to extremely sensitive info (yes, also have stuff on auto-delete). Complex passwords require a password manager - if those get updated and rooted then my yubico seems to save me again. In fact, with yubico I have a few passwords I memorized that aren't TOO crazy long - with a 2FA hardware key you may be able to SIMPLIFY passwords and still have good security. And the yubico is EASY! Clip it to your keychain and go.
• frei 6y ago
  The prescriptions in "If you’re a security conscious user..." make sense to me. If you use a unique password, sms/totp adds very little benefit. However the section for "If you’re a security conscious vendor..." doesn't make sense. Credential stuffing is so common, and sms/totp is a great tool against it. You could prevent users from setting their own passwords, but that seems a little "too different" from existing sites that it could harm usability.
• tbp105 6y ago
  I think this misses the point... do you need your own auth at all? Security is only as strong as the weakest link. If you have a "forgot password" that emails you a login or a "lost/changed phone" that removes the sms, don't bother even having the password or sms. Falling back to email means you've just pushed your auth behind the email's auth. Just use it directly by using oauth with google, o365, facebook or whatever makes sense for your target audience and be done with it. If you are b2b, use saml.
• haecceity 6y ago
  It could be used to deter users from making multiple accounts. It won't stop determined spammers though.