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Tell HN: SMS-based two-factor authentication is not secure
628 points by Zolt 4 days ago | hide | past | favorite | 282 comments
SMS-based Two-Factor Authentication is not Secure. I’ve read this before but brushed it off. It wouldn’t happen to me. It did.

I am with Boost Mobile. On Sunday night I received a text message that my PIN was changed. Within minutes I confirmed this to be true on my PC. I used the Boost application on my phone to change the PIN and received a confirmation text.

A few minute later I received a text message welcoming me to Metro PCS.

A few minute later I received emails to my business email that my account security information was deleted from my person email account. They used SMS authentication to my mobile number, that they now have control of to gain access.

A few minutes later I received an email there was an account recovery attempt on my coinbase.com account.

It took less than 30 minutes for these events to transpire.

I've spent about 15 hours trying to get my phone number and my email address back to my control.

I've accumulated a list of eight other people in the Boost Mobile Reddit.com forum where the exact same thing happened to them.

I filed a police report and filed a report with the FCC. I received a response from the FCC that they have started the inquiry and contacted Boost.

I finally did get my cell phone number ported back to Boost. I have not gained control of my Microsoft email address.

I didn’t realize I could only have messages of 2,000 characters. So I will wrap this up.

When account settings were changed, Coinbase gave me a link to lock my account, Microsoft gave me a link to log in to my account, which I no longer have control of.

Unlike competitors, which allow pins from 6 to 15 characters and for accounts to be administrative locked, Boost offers none of these options. The last Boost operator suggested I pick a more secure PIN.

I am calculating my losses and documenting all interactions.






Your problem is not with SMS as a second factor though. (Unless you think the attacker had your password as well). It is with the use of SMS as a single recovery factor.

The very things that make SMS a uniquely good second factor make it an awful only factor. Use of SMS for account recovery should in general (or at least for important accounts) have a delay (order of days) that allows the real user to intervene.


If the argument is "but you still have a password" it really kind of shows how weak SMS 2FA is. Compare that to a U2F token where you can very reasonably remove the password entirely and still be just as safe - it is itself just a strong auth mechanism, whereas SMS is adding extremely questionable value between the ability to phish SMS 2FAs or hijack the number.

Even in a situation where the attacker would have needed the password too, consider how much more vulnerable you are now that they have a significant piece of your auth - could they leverage that to social engineer an account recovery?

Phone numbers are terrible at conveying identity, unfortunately, so bringing them into the "who are you" heuristic is kinda just a net loss.


> Compare that to a U2F token where you can very reasonably remove the password entirely and still be just as safe

Yeah, and it requires me to use a U2F token, which I can loose, etc. You have to balance security and usability, and SMS as a second factor seems like a perfectly reasonable balance.


I'm glad someone is bringing this up.

I witnessed so many people lose access to their accounts because they wiped their phone that had an authenticator app, or they lost their physical 2FA tool.


2FA goes one of two ways:

1. You increase the risk of losing your entire life (if 2FA is properly implemented and avoids all social engineering process risks)

or

2. The 2nd factor devolves into a 2nd way to get access to your account

You really can't have both security and convenience.

> wiped their phone that had an authenticator app

try this one: battery dies in an iPhone. iPhone won't boot until battery is replaced. Battery can only be replaced at an Apple store. 2FA: do you feel lucky, punk?


Services like Authy address some of the loss of device issue, and always a good idea to have a backup token (e.g., yubikey) physically escrowed somewhere like a safe-deposit box.

But it is a whole lot of extra work to set up and maintain long-term, even with the best intentions.


+1 for Authy. Just get a used cheap Android phone for like $30 and use it as the backup device for Authy and never fear about losing your 2FA device again.

Does Authy actually offer 2FA? It sounds like the security boils down to your encryption passcode used to encrypt the 2FA secret, so you aren't actually using 2FA at the end of the day.

For personal use it probably is a good compromise for services which don't implement 2FA properly (that is to say, services that don't allow you to register multiple 2FA devices.) But realistically you might want to just disable 2FA and rely on your password manager.


Or just copy your TOTP codes to a second device without going via the internet.

I'm annoyed Google Authenticator makes it so easy to transfer accounts to a new phone, how will you know if someone's cloned your TOTP private key while you were sleeping?


Password managers such as 1Password and Bitwarden can save and fill in TOTP codes. Maybe not perfect security but a big win for convenience and loss prevention.

I have received advice from way to many people to not use your password manager as a 2nd factor be ause 1) It's actually become the only point if failure (your pw getting hacked). 2) Both factors protected and saved on the same spot

Mostly fear-mongering.

1Password in particular encrypts your vault with your master password and importantly an additional 128 bit secret key that is meant to be kept somewhere physically (e.g. in your safe). This key is needed the first time your vault is decrypted (e.g. a new device)

An attacker would need to have access to all of the following:

a) your encrypted vault

b) your master password

c) an 128-bit secret key

in order for the fears you've outlaid to be realised.

Really the only attack vector I can see is a physically compromised device (brute forcing is out of the question). In which case, they'd still need to somehow know your Master password and you're no more vulnerable considering your OTP is likely to be in an application on your phone anyway.


Since your own computer will typically have the vault unlocked, you don't need a+b+c. You can suffice with a circa 2000s Sony Music cd. Or any driveby malware, or malvertisement, etc.

Using the 2nd factor on another device as the first means attackers need to either compromise 2 devices, or compromise a single point higher up in the hierarchy (e.g., your google account).


Now we’re talking extremes!

If there’s malware on your PC that has complete access to your system memory you are screwed in every single way possible. I’m perfectly comfortable with having my OTP coupled with my passwords given this is the only real attack vector and requires an actively unlocked vault to expose secrets.

If this is the case, what’s stopping the malware from adding a key logger and MITMing your input to your bank’s website, Gmail or Coinbase?


I use BitWarden for my passwords while storing my 2FA backups in KeePass for exactly this reason.

I keep an old phone around with a duplicate Authy setup. I also photograph the 2FA code or QR code and print it to a safe place.

> I also photograph the 2FA code or QR code and print it to a safe place.

This is really great advice.

I do something similar. I have a copy of the recovery codes (where possible) in an encrypted volume with multiple copies. Also printouts. The printouts have saved me once already.

Also, don't underestimate the utility of carrying around an encrypted SD card with things you want to retain access to!


Don't most 2fa systems have recovery codes? You print em off or encrypt them with a one time password?

And the site has to support U2F. U2F is a great standard but almost none of the businesses I interact with support it. There are maybe 3 banks in the US that support it, but not mine.

I don't understand why banks and businesses don't outsource the whole authentication business to someone that does nothing else, and then does proper 2FA (maybe with a choice of security levels), and supports as many standardised solutions as possible.

One of the problems here is that few sites support U2F, and even fewer support it properly.

Proper support would mean allowing multiple tokens, so that you can have one permanently on your keychain, one permanently in your computer at home, and an off site backup pair that you rotate (enroll the one that is at home, then swap and enroll the other one).

On desktop, touching a U2F token is a lot easier than typing numbers from a SMS, and it actually protects against one of the biggest threats, phishing (the SMS does not - if the phisher bothers to ask for it, the user, who thinks that they're logging into the legit web site, will enter it).


You can also "loose, etc" the phone so it is equally weak on that front. Except the SIM can be hijacked, so SMS is strictly worse and never better.

Best compromise between usability, access and recovery is to always use TOTP but be sure to always securely back up the secret offline. Don't ever just scan it into a single device, as then you're back to being able to lose it and be locked out.


The advantage with the phone is that the web site operator can pawn off the difficult recovery part on your mobile provider (go there, show ID, get a new SIM).

IMO both the mobile provider and the web site operator should be jointly liable for damages resulting from SMS 2FA abuse. The mobile operator for giving access to your phone number to an unauthorized person, the web site operator for using a known insecure technique.

Both the number of successful hijackings and companies using SMS 2FA would drop drastically.


Its generally not "second factor authentication" but 2-factor authentication. The idea is that you have 2 separate authentication factors. Preferably both with decent security.

Besides, I don't believe coinbase does SMS only account recovery. So here SMS really did fail as a second factor. Since it seems attackers must have had a password and SMS. (I am not 100% on the coinbase account recovery process)


No, it sounds like coinbase used email recovery, but his email provider used SMS recovery.

So the hacker only needed to hijack his SMS.... with that, they gained access to his email, and then with that gained access to coinbase. No password required.


SMS is better than nothing, but you have a bunch of other better fallback alternatives before you should rely on it. You can support the enrollment of multiple hardware tokens (i.e., you keep one at home, and one on your person). You can have online push login approvals. You can have a TOTP code generator.

TOTP is the one that makes the least sense to me. It is also weak to phishing (extremely common) but adds protection against SIM-swapping (comparatively very rare). It also has almost all of the downsides of U2F (a pain in the ass if you lose your device).

TOTP has the downsides of U2F, but those downsides are comparatively easier to mitigate.

Put a plan together for the "house burns down" scenario.

With U2F I need to enroll multiple tokens and keep some off-site. So what does this entail? I keep maybe 3 tokens, two on-site that I add the new account to, then on a regular schedule I rotate one off-site and bring the third one on-site and go back through and add it to any accounts I've created in the meantime? The whole process is a pain in the ass, and not all sites allow multiple devices to be registered (e.g., AWS). And new accounts are still vulnerable during the time between registering and rotating the third key on-site.

With TOTP you can... just sync your TOTP database. Some apps such as Microsoft Authenticator do this on their own. Personally, I put all my TOTP secrets into a Keepass database and sync it off-site with Nextcloud. There is no way for the site to limit how many devices I enroll so it's easy enough to create as many backup devices as you need. If you're really old school, you can print the secrets and put them in a fire safe.

FWIW, I have several yubikeys. I primarily use them as a secure store for TOTP secrets and to store a SSH key (generated off-device and backed up), not for webauthn. It's just too annoying to deal with in a way that ensures I don't lock myself out of an account.


> a pain in the ass if you lose your device

Every modern TOTP app is cloud-synced, so I'm not sure why people are saying it's "a pain in the ass if you lose your device."

Heck, most modern password managers (e.g. 1Password, LastPass, etc.) are also TOTP, and help you fill the TOTP token (usually by putting in on your clipboard) at the same time they autofill the password.

> It is also weak to phishing (extremely common) but adds protection against SIM-swapping (comparatively very rare).

Sufficient paranoia / user training is enough to protect against phishing. (Especially for services where the only "users" are the extremely-paranoid IT admins themselves.) But nothing can really protect you from SIM-swapping, save for not allowing services that use single-factor SMS recovery to ever know your phone number in the first place.


> Every modern TOTP app is cloud-synced

I've got a few services that only support Symantec VIP, which does not allow you to extract secrets.

> Sufficient paranoia / user training is enough to protect against phishing.

Considering how easily actual factual professional security engineers fall for phishing, I don't believe you.


> Symantec VIP

See https://www.reddit.com/r/1Password/comments/8yey6y/how_do_i_...

(PITA, I know, but running little auth gateways like this is part-and-parcel of doing security for an org.)

> Considering how easily actual factual professional security engineers fall for phishing, I don't believe you.

It's almost always the service's fault for being designed in such a way that its real async user interactions are indistinguishable from phishing. You can't train a user to distinguish X from X.

• It's hard to train users to not forward TOTP tokens sent to them to someone else, if the real service will text or push-notifies the user their TOTP token "at random" (i.e. because the attacker tried to log in.) But if the service never does that — if you always have to go and fetch the token from your TOTP app — then you can just tell the user that the only time they are to go do that, is right after they've typed their username and password as part of logging in themselves; and that anything else is a phishing attempt.

• It's hard to train users to not type their username+password into phishing login pages, if the services you use constantly send you emails containing deep links. But if the service never does that — if the service always tells you to go your browser and navigate to the site yourself — then it's easy to teach users to never trust a login initiated through an email.

Security, in this case, is less about "good security hygiene", and more about priming/expectations. And because of that, the practice of being an IT admin for such an org, is a practice of picking services, or negotiating with services, to ensure that the service is following secure workflows when dealing with your users, so that your users can be trained.


I do use a similar approach to backup the Symantec secret - but what percentage of users do you think are capable of doing this? 0.1%?

> It's hard to train users to not forward TOTP tokens sent to them to someone else, if the real service will text or push-notifies the user their TOTP token "at random" (i.e. because the attacker tried to log in.) But if the service never does that — if you always have to go and fetch the token from your TOTP app — then you can just tell the user that the only time they are to go do that, is right after they've typed their username and password as part of logging in themselves; and that anything else is a phishing attempt.

A phishing attempt will do precisely this. You get a fake login page, type in your creds, and then you get a fake TOTP page.

> It's hard to train users to not type their username+password into phishing login pages, if the services you use constantly send you emails containing deep links. But if the service never does that — if the service always tells you to go your browser and navigate to the site yourself — then it's easy to teach users to never trust a login initiated through an email.

In a prior life I did some research on phishing. It is embarrassingly easy to fool even professional security researchers. Nobody is capable of consistently preventing phishing by using their own eyes and brain.


If you can manage a 100% policy of using no services that ever require users to do X, then you can also just disable doing X entirely through MDM. Phishing emails can't get your users if your users' email clients don't open links other than to whitelisted domains. :)

TOTP is an improvement over SMS in that identity is not tied to a phone number, which has been proven over and over again to be a terrible indicator of identity.

That isn't a meaningful distinction. Both cases involve you typing in a number into a web form.

It was a meaningful distinction to the OP...

While TOTP contains a bypass (phishing) SMS contains an additional vulnerability.


> You can support the enrollment of multiple hardware tokens (i.e., you keep one at home, and one on your person).

How many services do that today? And since so few people have fallbacks what is their recovery process like? Because the hackers will find the weaknesses.


WebAuthn explicitly tells Relying Parties (ie web sites) to all do this. All the services I use which offer WebAuthn or its predecessor U2F support multiple named hardware tokens and I enroll at least my Yubico branded device and one more at such sites. For those I use from a phone, the phone itself is enrolled.

AWS is the counter-example which will be (indeed already has been in this HN comment tree) cited as proof sites don't all do this, I've tried asking if there are literally any others, and never received any ideas. I don't currently have an employer and I don't use AWS for personal projects.

It's pretty common for sites that actually care about authenticating you (so, Google but not your Bank, GitHub but not your mortgage lender) to provide you with single use bypass codes which they tell you to write down and keep somewhere safe.


What about an authentication app? Google Authenticator or something similar can be installed on the phone which is necessary for SMS, improves the security more than SMS, and doesn't suffer from the problem of losing it, at least not more than SMS auth does.

When your phone is lost or stolen, you buy a new phone and go to your telco provider to get a new SIM with your number. SMS 2FA continues to work. Your Authenticator secrets are gone with the phone, and you're locked out.

(Unless you use a solution like Authy with multiple devices, which strikes me as the most sensible solution.)


It blows my mind that Google Authenticator still doesn't have a multi-device sync feature (or even a "recover from backup" feature on iOS for that app, because I think they added it recently to Android; just "recover from backup" alone would have been sufficient to convince me not to switch).

All of that made me switch to Microsoft Authenticator, as they do have both multi-device sync and "recover from backup" feature as well, so now I don't need to be stressed about my phone getting lost. Kind of sad, given that I've been a user of Google Authenticator for quite many years until that point.


I really wish that web browsers had worked on the UI for generating certificate signing requests and importing certificates and that websites had 2FA via username/password along with client-side TLS certificate for authentication.

This is more portable than U2F tokens since client-side certificates are part of the TLS standard and should be supported regardless of the application protocol used. Adding other devices could be done by sending a CSR along with the username and password and authorizing the second device from first device that's already logged into the account.


It had it! HTML 5 keygen tag https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ke...

But Mozilla, and Google double teamed to sink it in W3C to push their own bicycle reinvention attempts, which after 10+ years, multiple incompatible versions, and errata ridden revisions are still not there.

https://lists.w3.org/Archives/Public/www-tag/2015Sep/0001.ht...

Google needs to be kicked out of W3C


Yes! This was a very good solution. Built right into the browser, very convenient. We built a related CA product back in the 90s and were issuing client certs on smarts cards via the browser. Plug in smartcard and browser could automatically authenticate to all services. Take it out and go home.

I used an SSL CA (Startcom / StartSSL) that used Client certs as its (only?) method of authentication. It was a terrible experience if you ever had to log in from another browser.

I didn't know that. Oh, come on. That's so unfortunate.

> Yeah, and it requires me to use a U2F token, which I can loose, etc.

In which case there are much safer recovery mechanisms available. For example, a second U2F token, or handwritten backup codes.

> and SMS as a second factor seems like a perfectly reasonable balance.

My point is that it isn't. Unfortunately, today, identity is a true privilege - it pretty much requires purchasing multiple U2F tokens, and that's super shitty. That doesn't mean that SMS 2FA is a good idea - the fact that it can actually reduce your security is very problematic.


But that is my entire point. SMS as a second factor is purely additive. It cannot reduce security.

There is pretty much no form of second factor that users are worse at passing than backup codes. Even if people print them out (few do), they won't find them when the emergency happens. You need some form of trust that can be bootstrapped again from scratch.

For most of the world, SMS is it. The Nordic countries have the bank if system. But the market is too small. Hopefully the EU-wide identity verification systems solve the scale problem.


> Some form of trust that can be bootstrapped again from scratch.

This is not using it as a second factor. It is using it as the only factor. Having SMS as the only factor is not purely additive. As such it can (and obviously does) reduce security.

Account recovery is hard, SMS is quite usable there, but way to insecure to be the only basis for bootstrapping account recovery.


I don't really understand why you think I'm advocating for SMS as the only factor, when I very clearly wrote the exact opposite.

Let's say that you remember your password, but your house just burned down. You cannot replace the U2F keys and backup codes that were lost in flames. But you almost certainly can bootstrap your real life identity far enough to get a replacement SIM.

Which, in combination with your password, should be enough to get your digital identity back.


Except in practice, most providers (even those that should know better, like Google) allow use of SMS, ostensibly set up as a “second factor,” to be used for account recovery without knowing the password. Making it, in practice, 1FA.

Confusion about the word bootstrapping. I read "bootstrapping trust" as regaining trust based solely on SMS.

But indeed, sms as a second factor is much easier to recover in catastrophic situations than some other second factors. That is a fair point, and an advantage of sms over other common second factors.


> SMS as a second factor is purely additive. It cannot reduce security.

You are forgetting social engineering. Humans find it reassuring that the security process happened as usual, even if in fact the apparently "usual" process was them being being phished. This can mean they're actually less alert than they would be otherwise.

You get an urgent message from your bank about an unexpected $500 transaction, you follow the link & you need to enter your password as usual of course, and then it tells you that you'll get an SMS and to type in the code so you do so. Phew! Disaster averted! Right? This must have been real, you even got an SMS from the bank.

Alas the SMS was from your bank, and the bad guys didn't have a way to intercept it, but they didn't need one because you typed it into their phishing website. That unexpected $500 transaction wasn't real, but their emptying of your bank account will be.


Here's the same story without 2FA:

"You get an urgent message from your bank about an unexpected $500 transaction, you follow the link & you need to enter your password as usual of course. It was a phishing website. Your bank account will be emptied."

It did not reduce security.


But in your revised story I don't receive reassurance that everything is going as planned. That's what I'm getting at, the SMS step is reassuring even though it actually shouldn't be.

If there is no 2FA, not being asked for a confirmation code is things going as normal. Also, it's totally irrelevant whether the user gets cold feet since in the password-only world they've just handed away the keys to the kingdom.

> But that is my entire point. SMS as a second factor is purely additive. It cannot reduce security.

It most certainly can reduce security, that's the point. If I don't have a phone number on my account (which I almost universally don't) then no amount of SMS hijacking will ever matter.

If some provider forces me to put a phone number in, now I may be vulnerable to a weakness I didn't want to be vulnerable to. Maaybe today that particular provider uses SMS in a stricly additive sense. Maybe. Just as likely next month they'll redesign their site to be "easier" and add back the vulnerability.

Same with recovery questions. They make the security stricly worse for most people since they are password-equivalents with far lower entropy. Although personally my best friend from high school was named D3ho9WvylJkws1zfAKUxZjdYuCsS.


They specifically said "SMS as a second factor." What you're discussing here is a completely different different use of SMS that nobody is arguing in favor of.

As I mentioned, there is no guarantee any site is going to never allow use of that phone, once it's on file, to bypass authentication. Even if they don't right now. So adding a phone to an account increases your risk in a way you can't control. The only guaranteed way to avoid it is to never have a phone# on file.

> SMS as a second factor is purely additive. It cannot reduce security.

I responded to this in another post.

> There is pretty much no form of second factor that users are worse at passing than backup codes.

Agreed, I also mentioned backup U2F. At this point modern smart phones package TPMs that can also do attestation, so we're really not too far away from being in a situation where the vast majority of people have a U2F token in their pocket.


It can reduce security if password can be reset with SMS

That's the whole point of GP:

SMS is perfectly fine as a second factor, and terrible if it can serve as the only one factor.


> In which case there are much safer recovery mechanisms available. For example, a second U2F token, or handwritten backup codes.

Which have either higher costs or "administrative burden" or both which will lead them to failure for a big chunk of non tech-savvy people. Educating a casual user that they need to print out recovery codes and store them in a safe place it's not exactly top notch usability.


> Educating a casual user that they need to print out recovery codes and store them in a safe place it's not exactly top notch usability.

So then have two U2F tokens. Or use your phone's TPM as a U2F token. The usability of phone-based U2F is quite good.


A phone's TPM is the only U2F token that 99% of the world owns, assuming they own one at all.

Yes, as I've said, availability is the problem to solve. We should be shipping U2F tokens wherever we can. I'd like to see schools that require students to use GSuite and other U2F supporting sites giving students tokens for free. I'd like to see banks giving their customers tokens. I'd like to see companies giving them to employees.

IMO the problem is not "let's get some kind of 2FA" it's "let's get U2F in the hands of as many people as we can".


Most people don't own two phones though, and wouldn't think to have two separate U2F tokens.

> the fact that it can actually reduce your security is very problematic.

The only way it can ever actively reduce your security is if it's used as a single factor, as it was for the OP.


> The only way it can ever actively reduce your security is if it's used as a single factor, as it was for the OP.

I don't believe this is true. If I have your SMS I am considerably more likely to be able to phish a recovery, even if recovery also involves something else. Every piece of information the attacker can get is valuable for forging auth.

What SMS is good at is being available. At this point cell phones are distributed to a massive portion of the world. But at this point smartphones can also act as U2F devices, I believe, so I'm not sure that benefit is so meaningful anymore.

Instead of companies wasting time on SMS 2FA they should be figuring out how to help their customers set up U2F.

I'd like to avoid being in a situation in 10 years where we have great options for end users available but 2FA SMS is still supported for legacy reasons, and unwitting users end up using it because it seems easier and they don't understand the risks.


> I don't believe this is true. If I have your SMS I am considerably more likely to be able to phish a recovery, even if recovery also involves something else.

So it's better to not consider that information at all?

What is better? (1) Requiring a password to login or (2) Requiring a password and a code sent via SMS?

The problem you're describing is that services accept SMS in leu of other forms of verification, such as an actual password. Personally, I would very much like it if I could turn off any and all forms of "I forgot my password" flows. There should at minimum be a one-week waiting period or similar.


> So it's better to not consider that information at all?

Exactly

> What is better? (1) Requiring a password to login or (2) Requiring a password and a code sent via SMS?

They're equivalent in my mind - SMS is such a weak 2FA mechanism, and it's so easy to get wrong and have it decrease your overall security, any benefit is lost. Rather than pushing SMS because it's what we have we should make greater efforts to leverage technology that we know is considerably better in every regard except availability today - IMO that is the problem to solve.


SMS adds friction to password stuffing. Given that a gazillion people do not use unique passwords, this has some value.

It is possible that if we spent more time as a community encouraging the use of password managers that the net improvement in security posture would be greater, but this does remain a nontrivial benefit of SMS.


If you have strong generated passwords that are different for each system and you use password manager then you would not need 2FA at all. Well maybe if it is for system that stores your password in plain text but who would be stupid to keep user password in plain text and slap 2FA on top of it.

U2F and 2FA came to life just because people are bad at making passwords and remembering them.

Making non technical people to use password manager with generating passwords for each page is still hard.

Making non technical people use SMS as a second factor is easy.

Making non technical people use tokens is still hard.

There is a lot of value in having SMS 2FA still, yes you can phish it or you can hijack the number. But that is argument like: "there is no point in having any security at all because if you install malware on your computer you will get hacked".

Yes SMS alone is not going to save you, but people have phones and understand that they type code that comes via SMS to the phone number they provided when registering. Barrier to entry for it is so trivial that I think it still has value.

Barrier to entry to take over someones phone is not high but random kid on the street is not going to do that just like random kid that can find your email + de-hashed password from database dumps.

If you have someone who is motivated to get you then probably given enough time they will get you anyway.

So take into account what that SMS 2FA prevents and what issues it is solving. Don't just throw it away.


Hahahaha you would be surprised my current employer is thinking of introducing 2FA and yeah every pass is stored in plain text. I've been trying to make them change this for years, also the passwords are limited to 20 chars yeah.... security is shit here

Just to add to my comment:

It might be confusing but that was account recovery attack.

For account recovery there is no "password" as thieves just made their own password while having victim phone number.

So phone number as a password recovery option is not secure without any additional checks. Not 2FA because with this attack there was no second factor.


> Compare that to a U2F token where you can very reasonably remove the password entirely and still be just as safe

Not only that, but you can remove the username too: WebAuthn supports a "usernameless" mode where you press "login", touch your authenticator and you're in.


But that isn’t portable. If you lose your device or just reinstall the OS, you can never login again.

Sure, but that's why you add multiple devices/keys to your account. Reinstalling the OS should be fine.

I'm very much looking forward to password managers acting as soft-WebAuthn tokens so they can hold a simple private key and log you in to sites automatically by answering the login request. That way, you only need to unlock your password manager and you can log in to any site without a u/p.

Just don't get your password manager stolen, I guess, but that's already the case.


Are we comparing it to a token though? Or are we comparing it to nothing?

I want warn people about U2F.

U2F is only an authentication tool, not security/encryption one.

If you have your smartphone/browser/pc pwned, you are even more screwed than with offline key table/token.

For something truly security critical, you need security against MITM on your own device, which only leaves smartcards as an option.


You can only use a U2F token at the only factor when it's acceptable for you to temporarily lose control of the account.

I've posted before on here about my experience getting SIM swapped and how quickly someone was able to gain access to a bunch of my accounts. If I hadn't been at home and looking at my phone while it was happening, it could have been much worse, but thankfully I was able to get in and terminate most of their login sessions before too much damage was done.

The one thing I distinctly remember was two of my GMail accounts starting the recovery process. Thankfully, that process apparently gives either 14 or 30 days to stop the recovery and secure my own account. Had I not been connected, that may have been my only saving grace, as I was able to secure those accounts and subsequently use them to recover other compromised accounts.

The larger lesson for me was to always use TOTP tokens where possible over SMS, and to completely disable SMS recovery for accounts that didn't have a delay on SMS-only recovery.


This. SMS is a great second factor and is perfectly suitable to prevent the main attack that you want second factors to prevent: that is if your password appears in a password list for any reason it should stopp anyone from just running away with your account. Note that if you are targeted directly SMS is not going to help you much but in this case maybe your password can (depending on the capabilities of the attacker).

Now is SMS the best second factor? Of course not and a proper U2F token will be a lot more secure in many cases but for most people SMS should be perfectly suitable. All this of course requires the auth provider to be somewhat competent and not use SMS as an only factor in any circumstances.


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.


The 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!"


SMS 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.


Basically every service I've used that requires SMS will use it as the sole authentication factor for resetting your password.. It's brutal

I 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.


What's the recovery process when your phone gets stolen, or you drop it?

For 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.


A 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.


If 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.

You'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.

Except 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.


But 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?"

You're incorrectly assuming that you can predict a site will never allow password reset via SMS only.

You can check if they appear to allow it today. Not perfectly, as they may have multiple variants and depending on other factors you might get presented with one or the other.

But you have no way to predict if next month a PM there decides their current password reset was too cumbersome and they change it to SMS-only. If you had a phone# on file, you're now suddenly vulnerable.


others may have suggested that, I did not :)

> 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".


It 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.

The 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.


Again, 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.


Twilio, Kraken, Paypal, Gusto, Bittrex, Coinbase, ...

But none of these support U2F or WebAuthn at all. The problem isn't that they need to support "multiple" tokens except in the sense that they don't support any at all.

They all support TOTP and some (such as Kraken) support U2F.

Point is whether it's U2F or Web'n'Auth or TOTP they need to support multiple keys.


Kraken's own support site says that they do not in fact support U2F.

https://support.kraken.com/hc/en-us/articles/360001363963-Yu...

It doesn't make sense to try to "support multiple keys" for TOTP. You can copy-paste TOTP seeds if that's what you want and feel comfortable with, if the site tries to allow you to use any of N seeds they not only increase their system complexity they also reduce their security by a factor of N which makes no sense.

Edited to add: OK, Coinbase does now have U2F and they clearly state you can use "a maximum of 5 keys" which feels like that's enough.


Assuming that the sites allow you to change the token manually?

I'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.


TOTP is phishable, which is a way way way more common attack than sim swaps.

Sure, no security measure is perfect. Hardware tokens are likely to have better properties than TOTP, which has better properties than SMS, which has better properties than nothing.

you can phish SMS exactly the same way you can phish TOTP, I'd say :)


TOTP is marginally safer than SMS.

It also comes with large downsides. Security is an economics game. Marginal improvements in security posture are not always worth the cost.

There are a bunch of people who insist that web services should drop SMS completely and demand that all users use TOTP (at least). I question the value of this change given that TOTP only protects you in comparatively rare cases.


phishable how? "your account has been hacked, please provide us a TOTP code"?

1. 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.


This is certainly a vulnerability, but it also depends on how you get your TOTP codes. I use Bitwarden's browser extension to get mine, and if the domain is incorrect, the extension won't present me with the code. I think this is a decent level of protection from phishing.

I encourage you, as an exercise at least, to think about what you'll do when it doesn't work.

You're sure this is the right web site. But Bitwarden won't fill out the code. What could be wrong? Did the idiots who make this web site change the URL?

Now, maybe you're a far above average user and you would calmly determine the exact cause, assuming at every step that the most likely explanation is you're being phished. Hopefully that's more likely now that you've done this exercise. I would love to believe I'm in this category.

But most users will just be frustrated, why wasn't it filled out? Is there a way to get the code from Bitwarden anyway? There is, it's a bit fiddly but you can do it. Lots of users are going to do that. They might even help each other to give their credentials to bad guys, community spirit.

Hopefully some of those users pause because this is unusual and a few of them will realise in that moment that they're being phished. But experiments suggest most won't.


I did consider this, and I would also like to believe that my first thought would be "I am being phished" rather than "I'm sure this is the right web site." I do understand that many users (including myself on a bad day) might not recognize a phishing situation. But at least there is a layer of defense that SMS doesn't have.

Maybe the Bitwarden extension should warn users when they try to copy/view a TOTP code by searching for a login rather than using a matched entry.

U2F is my preferred method of MFA, but many services don't support it, and there can be practical issues even for the ones that do. For example, some services support U2F in a browser but not in mobile apps.


Couldn’t this entire scenario play out exactly the same with SMS codes?

Yes.

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.


TOTP 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.

Sure. I'm not opposed to supporting it. It is just weird to me to see people pushing for it with seemingly equal vigor as U2F.

SMS is not a good second factor, even as a second factor.

I deprecated SMS 10 years ago and the only way I receive SMS codes is via an online interface that is password access.

For most people, SMS fails miserably when you need to change your SIM card or fly to another country, or work out of a place with no cell reception but has wired or wi-fi internet access. That's a big part of the reason why I deprecated it in favor of e-mail, which works flawlessly anywhere in the world you have an internet connection.

I only support U2F or TOTP based 2FA and it's upto providers to get with the beat if they want me to use real 2FA.


How do you direct SMS to the online interface?

Twilio

Exactly this. Here in Israel, SMS is used extensively as part of a multi-factor authentication system. I also require my National ID.

To move my phone number (consent or not) between any phone companies requires an SMS, my National ID, and verification of my ID, and personal details in the government database.

SMS by itself is not secure.


You can’t control some random guy in a provider store giving out a new sim for your account, whether maliciously or because they were deceived.

And still numbers are being hijacked even in Israel [1], and even in Sweden, where I live now, I swept my SIM without my ID being properly checked

[1] https://www.gov.il/he/departments/news/sim


Absolutely. This is the problem - it's not the ideal method.

This always bothers me. People say "SMS-based 2FA is bad" and then all the reasons they give have nothing to do with 2FA at all.

The option for a delay of is great. The option of adding a custom security question/password etc. is even better. The option of completely turning off recovery is also great. The ability to have your solution on multiple devices without a need for a mobile phone number based recovery is great as well.

I hate it that Twitter forces you to enter a mobile phone number even when you set up an authenticator code generator as 2FA.

Oftentimes the weakest link in most of these services is the account recovery part.

When we set up the self service account recovery in saas pass password manager and authenticator we added all of these customizable options to mitigate against potential SIM Swap attacks.


On Twitter you can remove your phone number after the fact tho. In fact most sites that req a phone number to sign up etc allow you to remove the phone number later if you choose.

I got my Uber account taken over this way and I wasn’t using my cell for recovery of anything. SMS is terrible for all these purposes

> The very things that make SMS a uniquely good second factor make it an awful only factor. Use of SMS for account recovery should in general (or at least for important accounts) have a delay (order of days) that allows the real user to intervene.

No, SMS shouldn't be a single factor, period. It doesn't prove much, and is insecure, as the current post shows.


SMS will remain vulnerable as long as the mobile accounts that hold them upstream remain vulnerable.

One option I’ve heard might be different is to not your your mobile sms on accounts, but to get a voip based sms number. It might leave things at the mercy of a different system but the footprint might be different.


I've tried this, but many companies block VoIP numbers for MFA/2FA. Some don't. This works with LinkedIn, but not any companies I have purchased things from.

This kind of arrangement is often mockingly, but accurately, called 1/2 factor authentication.

I sympathize with the user.

It's a little mind boggling though. Securing money with a $15/mo phone plan. It's an extremely ghetto phone service. If anyone's to blame, it's Boost Mobile. Cricket Wireless. Pay for a major carrier plan.


There is no situation where it is good at anything.

I lost my Microsoft account years ago. I still get emails from Microsoft stating that there's suspicious activity on the account. I got two just yesterday.

Despite that, despite still having access to the email the account is on, I cannot recover the Microsoft account. Despite Microsoft notifying me that the account is still, years later to this day, being abused, cannot use any form of recovery. I cannot access the account with help from support or even after visiting a brick-and-mortar store.

It's one big reason that I've long since refused to purchase anything more from Microsoft and have ditched Windows.

Good luck recovering your stuff.


>Despite that, despite still having access to the email the account is on, I cannot recover the Microsoft account. Despite Microsoft notifying me that the account is still, years later to this day, being abused, cannot use any form of recovery. I cannot access the account with help from support or even after visiting a brick-and-mortar store.

This happened to me. I was briefly a contractor at MSFT and was able to escalate the issue -- after a few years, these accounts get automatically deleted. It's likely that your account is completely wiped and no longer exists.


> It's likely that your account is completely wiped and no longer exists.

If that's the case then why do I get emails notifying me that unusual sign-in activity is occurring? And, why am I unable to create a new account with the same email?


google does the same thing

Protonmail is the best beacause it does not require backup emmail or SMS, just the username and password and 2fa being optional (but you must have the password), which is how it should be. So many people have gotten hacked through phones and or recovery emails.


In the same boat. Really annoyed I can longer access it. The process to recovery is a total joke too.

As others have said, it is not that SMS 2FA is insecure; it is that thieves have figured out how to defeat it using SIM jacking and a bit of facebooking and googling. It is now trivial to figure out your home town, your favorite pet, etc. Also as others have said, the current alternatives have their problems. What if you lose all your Yubi keys? What if your phone was accidentally wiped and you never got around to backing it up? You cannot prove you are you and so customer support cannot help you. Google, Microsoft, and Apple are not known for helping consumers get themselves out of this catch-22.

It is a mistake to ask consumers to protect, backup, and secure their digital lives themselves. Consumers don't have the time or skills to keep up with the hackers. If Apple, Google, ATT, Verizon etc. cannot provide digital security, this is an opportunity for someone else to step in. My personal suggestion is this is a ripe opportunity for someone like the US Post Office or Department of Motor Vehicles. Consumers would go to the US Post Office or DMV and purchase a Yubi key from them. The additional value they add, is they can verify the identity of the consumers who is purchasing the Yubi key and replace the key if it is lost/stolen. Similar to how they process driver licenses or passports. This service is optional and would actually cost money. I would gladly pay a monthly fee for this peace of mind.


> As others have said, it is not that SMS 2FA is insecure; it is that thieves have figured out how to defeat it using SIM jacking and a bit of facebooking and googling

Uh... what does (in)secure mean to you?


exactly. "its not that the lock is insecure, its just that sometimes thieves figure out how to make keys."

What I mean is that if thieves can defeat the lock on my door, it doesn’t mean my door lock is worthless. I still lock my door but I don’t rely on it exclusively for protection.

> As others have said, it is not that SMS 2FA is insecure; it is that thieves have figured out how to defeat it using SIM jacking and a bit of facebooking and googling

It is 100% insecure, and been exploited for nearly a decade.

1. Anybody with access to raw SS7 network can basically click a finger, and have you traffic rerouted

2. GSM interception gear is widely available

The person who invented "SMS verification" was a round idiot


Absolutely this, but the service should act like a driver's license if you want people to actually use it.

Pay some $ for the key, renew it every 2 years for a fee, pay for a replacement if needed.

No one wants another monthly fee, taxes should keep the infra up like any other license.


We have something vaguely similar with "BankID" in Norway. It's a bank issued digital ID that submits a 2FA to your phone (not through SMS, but through some other system that takes over the whole screen - not sure what it is).

It's usable for almost all government agencies or official stuff online here, but I haven't seen anyone use it for third party auth as it costs roughly 10 cents per login for the service using it.


This has been rolled out and in use in British Columbia, Canada as well. We have a digital ID app for iOS and Android, which you verify your ID with first, then for government sites (e.g., health records), you login through this app instead - there are no emails, usernames, or passwords involved.

From a usability standpoint it's not very good though. The experience differs from phone to phone and it kinda feels like a hack from a programmers point of view.

In Norway, Sparebank1 is pushing an app to get one-time codes now. I wonder if we'll see more of these in the future?

I use the Microsoft authenticator to get access to my Microsoft work account.

I bet if everyone starts making their own apps for one-time codes EU will demand a single app to do all of this.


>not through SMS, but through some other system that takes over the whole screen - not sure what it is

This sounds like it might be a so-called “flash” SMS. https://en.wikipedia.org/wiki/SMS#Flash_SMS


I only use 2FA if the service provides me with backup codes that I can put in my password safe, which has a unique, long password that is stored and backed up in several places.

If there is not a self-service recovery option for me losing my phone, I won't use it.

---

FWIW I keep a copy on my desktop and on my phone (Keepass) and sync them every few weeks. I try not to add new passwords to my phone copy in order to keep things simple, but Keepass can do diffs and merges.

"But if your safe is owned, then all your accounts are owned!" Yes, that's the balance I take. If someone is able to get my safe and use my bio auth on the phone OR otherwise crack it, I'm screwed.


> Consumers would go to the US Post Office or DMV and purchase a Yubi key from them.

> The additional value they add, is they can verify the identity of the consumers who is purchasing the Yubi key and replace the key if it is lost/stolen.

This is exactly how digital signatures work in my country. A government institution vouches for digital certificate companies which verify and certify people's identities. It can be used to file taxes and lawsuits, for example. To most people this is just yet another layer of bureaucracy.


What really grinds my gears is the seemingly unstoppable global transition towards SMS to a mobile phone number as means of identifying an individual, conflated with "security" through 2FA/account recovery, with this as the only option.

This is especially popular within Fintech.

Wise (formerly Transferwise) recently started requiring 2FA for signing in - SMS is the one and only option. Revolut requires it for acknowledging transactions and changing/viewing debit card info.

That legacy banks do this is expected, but I'm really concerned about this trend among newer global and big actors who otherwise present themselves as modern.

I strongly urge other users here to reach out to customer support of these companies and request them to supplement this with some other more secure means of 2FA, such as TOTP (hey, we gotta take what we can get), U2F, or Webauthn.


Well, the European PSD2 has forbidden the use of SMS TANs last year for banking applications while requiring much more stringent 2FA use (for account balances more than 30 days in the past for instance).

So, I would say quite the opposite to unstoppable.


And because it has not required some open standard as a replacement, I now have hundreds of MB of different bloatware bank apps on my phone, each of which I have to use in a slightly different way when logging into my bank accounts, usually with scanning barcodes or remembering yet another PIN. Migrating to a new phone is a nightmare.

For extra convenience, PSD2 also mandated a logout after 5 minutes of inactivity.

Some of the ideas behind PSD2 are great, but the outcome is about as good as the cookie directive.


Absolutely agreed. I expect consolidation to happen in the next couple of years on this. Banks who do it well, will win customers.

I've only seen it get worse, and I don't expect that to change.

One of my apps where I spend money on a regular basis (always similar small amounts, always from the same phone, usually from the same IP) constantly triggers 2FA via my banking app. Even as an informed customer, I have no idea whether to blame that app, their payment gateway, Visa/Mastercard, or my bank (that issued the credit card) for that bullshit.

The previous situation (banks absorb the fraud) seemed much better for me as the customer, and banks stuck with it. PSD2 made it so that customers can't pick their bank based on which is more convenient, by making them all at least roughly equally inconvenient. Few people will bother to change banks over this, and even fewer banks will feel enough pressure to actually improve.


Yep, and the banks are literally reaching the deadline as we speak. All my EU banks are notifying me that within a week or so the SMS codes will stop working, and their mobile app will be required for 2FA.

Super annoying, especially when (prior to the pandemic) I traveled a lot and had a new SIM every month or two. Insanity.

Wise supports 2FA through their app (similar to what Google does, with a prompt).

That isn't 2FA. That is a single factor recovery process. SIM-swapping only defeats SMS-based 2FA if the attacker also has your password, which is difficult to accomplish if you are using good passwords that are unique.

I had to remove this detail from my original post as it was too long:

Boost mobile is negligent and not following industry standards. Their whole security model is based on a 4-digit pin. At first I thought somebody had a script working its way up through all the combinations at the login screen, but I no longer feel that is the case. The fact that at least nine of us had this same issue within days makes me think there is a wide-spread issue here.


I don't have a source to hand, but I've heard from other post-mortems that in SIM-jacking attack the carrier has been socially engineered into not bothering with the pin, ongoing court cases RE negligence perhaps on-going.

If they're able to issue a new SIM card without the system requiring them to enter the PIN first, then it's a very terribly designed system.

They have to be able to issue a new SIM card without a pin in the case of a lost phone though. In that case they should probably check government identification, of course, and not be available remotely.

I thought you needed the PIN if you wanted that, too? As in, if you lose your phone and don't have the PIN set up with your carrier, you've lost your number and can't restore it.

That would mean eventually there would be no phone numbers left for anyone.

No, that would mean they would eventually disconnect the service on that line for non-payment and give that number to a new subscriber.

The "industry standard" is that SIM-swapping it not difficult. Arvind Narayan's group at Princeton demonstrated this pretty convincingly. This isn't unique to Boost.

Does coinbase really allow account recovery with just an SMS? It seems to me like the attacker must have had more than just control over your SMS number.

Yeah the attacker now also has email control.

Maybe it would make it more clear that this was not 2FA attack.

It might be confusing but that was account recovery attack.

For account recovery there is no "password" as thieves just made their own password while having your phone number.

So phone number as a password recovery option is not secure without any additional checks. Not 2FA because with this attack there was no second factor.


Remember that there's also the traditional way of pulling this off, which is to pay someone at the phone company to do things in their support system for them.

With just a SIM swap, isn't it possible for an attacker to reset the password on your main email account (e.g. gmail) via the phone, then from there reset the password on your money account through the stolen email?

Sorry you went through all that, and even more sorry that you'll probably be dealing with the fallout for quite some time.

I agree that SMS 2FA is not secure and a terrible idea. I've moved countries and my old mobile number has been given out to someone else. I don't even know what accounts I have might be tied to that phone number and I don't have any way to find out.

I have had friends message that person without knowing it as well. He could easily impersonate me on WhatsApp and fish for my personal info from those contacts.

Luckily, he seems to be a decent person but I not only have to trust this stranger to be honest, but also need to trust that the number stops at him or goes to another honest person if he drops it.

Phone numbers are not identity and using it for verifications of this sort is a horrible idea.


Part of the issue here that I don't see people addressing is that SMS as an only-factor recovery tool is often not optional. I hit a case like this just the other day: the service would not allow me to log in at all without adding an SMS number. This is becoming increasingly common.

The irony is that my security is now worse. At least my password was randomly generated.

I'm not sure what there is to do about this, other than educating as broadly as we can and hope that engineers advocate in their own organizations to change this.


I really hope that I am not the only one requesting businesses to not do this when I encounter it. It may be the only way to get it to stop.

Open a case with customer service and represent it for what it is; a security hole that prevents you from using the service.


that is because google and other companies derive more $ from your number than protecting your privacy/security

Google doesn't require SMS. They often ask me when I log in, but I can always hit 'skip', which I do because I'm scared of this exact case.

This is not universally true. If Google decides that your account looks suspicious, either at creation or a later date, you are unable to access it until you provide a phone number.

You also used to be unable to set up a U2F/FIDO 2FA without first setting up SMS 2FA (but you could delete the phone number from the account later). Not sure if that's still the case.


Not only is it not secure, it's not a constant for everyone.

I moved countries and I am now locked out of my bank account abroad since they verify logins via OTP over SMS.


I've signed up with voip.ms, which provides me a pay as you go sms number for basically $0/mo. since I only use it for auth.

Many services go out of their way to detect and block the use of VoIP numbers for SMS auth :s

I consistently use voip.ms for auth codes from my bank (TD), Whatsapp, Signal, and more that I'm likely forgetting. Highly recommend them.

What's the reasoning behind that? Maybe to prevent bots?

I'd start with VOIP numbers being so easy to spoof... and move onto the entire telephone network being insanely insecure and unverified, despite decades of efforts to link people to telnos -- until they implement actual caller-recipient full verification, they've effectively got nothing.

> until they implement actual caller-recipient full verification

Is it even possible to do this at this point? I'd expect something like this to fundamentally change the way telephone networks work.


Not sure how fundamental it is, e.g., is it fundamental to bar ad-hoc caller-ID functions and require displaying the actual number & name of the account (maybe allowing additional info also)? Telcos already pass on this info - how big a deal is it to transmit accurate data?

But even if it is fundamental, such fundamental change is needed.


Maybe look into whether you can get a Skype number set up to receive the SMSs. Some countries/banks will work with this arrangement.

But I feel your pain. It is very frustrating situation to be in.


For some countries (USA) you can forward your number to a google voice number and retain incoming sms. Call forwarding isn't possible to my knowledge.

Porting my number to Google voice before moving abroad was one of the smartest things I’ve ever done (in hindsight), for this reason.

I sometimes wonder why Google has kept it running for so long, when they’re so keen to kill off boring, under-performing products.


Why cancel your old phone number in that country when you still have a bank account there?

I suggest a bank which doesn't suck, such as bunq.


It can be costly.

I moved from Ireland to the US and kept my Irish number active - the cost was a €5 topup every 6 months.

Going in reverse is much harder - a lot of the budget phone providers in the US don't have any roaming offering. Best I can tell, you really need to have an account with a real provider, and that realistically looks like $20/mo (Google Fi), 20x more expensive than the reverse.


Then it sounds like changing bank is a better answer for many.

This oversimplifies the situation - if every US bank uses SMS and you want to retain a US bank, what do you do?

That's such a huge "if" that an alternative immediately came to mind:

TransferWise doesn't require a US phone number, but you can have a US account number with them.


Maybe they didn't know they needed a phone number to maintain access to the account?

Let's not blame the victim here.


The bank is at least equally at fault, if not more so.

I would never think my phone # was the only proof of identity.

If that's what your bank had been using during the login flow...

if you immigrate, like I did, but still have some pension funds or saving accounts in your home country. Why would I want a local phone line?

So your bank can send you the SMS you need to sign in (which in itself indicates their security is poor).

most banks don't support international numbers if that what you meant

No, that's not what I meant.

what did you mean then?

Banks which rely on SMS 2FA should not be trusted with your money.

I forgot to include this in my original post. I use the Microsoft authenticator application to authenticate my account. My mistake was also including my mobile number as an alternative way to authenticate my account. I don’t know if I was aware of this or if Microsoft prompted me for my phone number at one time and I did not think through all the ramifications.

We set up multiple different types of recovery and backup and restore options for the saas pass authenticator and password manager to let you the individual be able to customize it as you wish.

The threat model is increasing for personal use as solely SMS based account recovery is becoming more widespread. The increase in crypto usage is another accelerant.

Good luck solving this unfortunate incident.


Got an email from Heroku last night saying they're discontinuing SMS as a 2FA scheme... yay Heroku!

Yep. They've been planning that for awhile, hopefully a case of "leading by example". For me hardware keys (U2F) with TOTP as a backup are really essential. I've purged SMS where I can. Unfortunately, too many (like banks) have stopped at SMS and email as options -- and that only recently. My (insert name of wildly popular open source password manager here) vault is secured by U2F with TOTP as a fallback, and I use its TOTP feature to secure logins for less sensitive services. Someone mentioned building in delays for resets: that's actually how both the US IRS and Social Security roll. Last time I reset SSA I had to wait for a physical letter with further instructions. Inconvenient, but probably a step in the right direction. If government intel agencies weren't so uptight about crypto, we could all have our own officially issued crypto keys by now. But no. The prols can't be trusted -- and don't deserve it anyway.

For whatever it's worth, the US government has shown itself to be spectacularly bad at keeping secrets (proof left as an exercise for the reader).

Making existing accounts less secure by removing a second factor is not “leading by example” in my book. Just make me pick a different second factor on my next sign-in.

Not sure if the yay is sarcasm. Heroku will remove existing SMS as second factor from all accounts, effectively making those accounts less secure. Yay Heroku! (Sarcasm intended)

No sarcasm intended at all on my part -- I think this is a very good move.

SMS is very bad as a 2FA, in that someone can fairly easily social-engineer your phone company to send them a new SIM card for your account, and once it's in their phone, all your SMS messages go to them. They now have control of your "protected" account (and yeah, they have to get your password as well, but if you're a big enough target, it's worth it).

This is why getting rid of SMS entirely as a 2FA is seen as an improvement in security.


Removing 2FA from existing accounts is never an improvement in security. As other replies on this post have noted, having SMS as 2FA is always better than not having 2FA. Heroku is actively harming their user's security by removing 2FA from user's accounts. Some users will not set up a new 2FA method on their account, leaving their account vulnerable to password attacks.

Unless they are requiring everyone to use 2FA, isn't that objectively worse than having the option of SMS 2FA? I'm sure there are a significant number of people who would just switch back to using a password instead of SMS 2FA rather than having to get a non-SMS second factor, since it is much less convenient than just putting in a phone number.

Well... I think that if they don't require 2FA, then, well, they don't require 2FA, and not having SMS is neither worse nor better.

If they do require it, then I believe the consensus is that 2FA via SMS is a very bad choice. And since Google Authenticator (and other such apps) are free to download and use, it's not really a burden.


SIM jacking is pretty easy. In Australia if you know someone’s mobile number and date of birth you can port a prepaid mobile. For postpaid accounts all you need is a bill.

The barrier is higher than random automated port scans but the value of being able to get access to financial accounts is high enough to justify the investment.

I use Authenticator apps wherever I can. Where I can’t, I use a completely private number for 2fa (I run a virtual number product that is like Google voice for Australians to do so http://www.benkophone.com)


I made a point about this previously and unfortunately, your situation is exactly the reason why SMS authentication should be avoided, since these sort of attacks are now becoming common. [0]

[0] https://news.ycombinator.com/item?id=27311641


Nothing is secure against a determined targeted attack. That's why we have layers of security. SMS 2FA adds a layer of protection against random attacks, and for that it works great. It should never be solely relied upon for high value accounts.

I think crypto companies should block withdraws for a period of time after a password recovery.

(OP, you are calculating your losses, but didn't specify what those losses were. Did the theif get your crypto?)


I have not regained access to my bitcoin account, in part because I have not contacted customer support to do so. I’ve been too busy regaining access and continuing to support my client base.

My account is locked, and I am pretty sure my funds are still there. It will be a significant loss, but not devastating as this was my non-primary investment account.

I still don’t know the full extent of my losses.

So far, my losses are primarily loss of billable time. I am not a litigious person, but I am also going to educate myself as to what ‘pain-and-suffering’ means. Both my personal and business bank accounts are ok. I now understand why banks do not use email addresses as the login id. The thief would not (easily) be able to align my email address with my bank login id.

Once through this, I plan disassociate any portion of my login id with my name.


If your crypto was stored on an exchange then this is par for the course; rule number one is that if you don't control the private keys, the coins are not yours.

You haven't even tried to regain access to it? Instead of spending time on HN you might want to reach out to Coinbase.


Agreed. Done. "Thanks for taking the time to contact us. We're currently receiving a high number of requests so we may take longer to respond, but our team is working hard to get to every inquiry quickly."

> I now understand why banks do not use email addresses as the login id. The thief would not (easily) be able to align my email address with my bank login id.

This is an important point and one I've been thinking about for years. There's so much discussion about using password managers and good password practices and 2fA but almost no discussion on how using a single identifier to log into all these various services is in itself a huge security vulnerability. If we had different login usernames for each service, gaining access to people's accounts would be that much more difficult.

Email should be reserved for communications and not double as a means for authentication.


Or get a domain with catch-all, and a different email for every service. Ideally not trivially guessable.

Coinbase has extensive access to mobile provider data. They can see when number ported and what phone the thief uses, but it's really hard to make decisions.

I understand that it's hard in the edge cases, but a port followed by account recovery within a short period of time should be enough of a red flag to immediately lock the account.

> A port followed by account recovery within a short period of time should be enough of a red flag to immediately lock the account

What happens if a legitimate customer's phone gets lost and they quickly transfer the number and reset their accounts?

I think they should do a video call verification.


If a customer loses the phone, and then ports the number instead of replacing it, and also forgets their password at the same time... yeah, I think it's fair to give them a bit of a hard time before letting them in.

Video verification sounds reasonable, as would some wait time. What's not reasonable in that situation is a self-service fully automated account recovery via SMS and e-mail verification followed by allowing withdrawals.


i thought coinbase did just this.... either made recoveries a multi-day thing, or disallowed transfers afterwards. maybe that was blockfi.

This is really interesting because of a few things:

* SMS authentication is not the same thing as 2FA, but people think that it is.

* SMS account recovery is convenient for the bad guys.

* The fact you got a welcome text from Metro PCS. If that was sent to your Boost device, someone from TMobile (they operate the networks that both Boost and Metro ride on) needs to take a look as that should not have been able to happen.

* In order to port a number you have to know the account security question's answer. Boost does have this. Was this bypassed?


Recently Mozilla started requiring 2FA for their AMO site used to publish addons. I have a few private addons that I develop and use, nothing big yet, but I really didn't want to link anything up with 2FA over SMS and I'm also trying to reduce my "Google footprint" so instead I selected their only alternative that doesn't use a centralized third party.

It was a bit complex, but I eventually got Keepass to generate the TOTP codes which so far are pretty awesome.


For anyone in the US wondering, Ting and Google Fi both allow authenticator-exclusive 2FA. I’m very happy with Ting.

But the banks and crypto exchanges are blocking VOIP numbers like Google's

Very true.

I think it's a shame most banks (at least here in the UK) implemented 2 factor auth with sms only just to comply with "strong" auth regulations.

Authy on your phone or multiple u2f tokens are definitely better than SMS.

I wish computer manufacturers started including tokens with computers, so that at least people would start using them.


It's a major issue in South Africa too with bank accounts being raided.

Bank says not my problem if your password got compromised. Cellphone provider says not my problem - SMS was never advertised/intended as secure.

So the user just has to deal with bank account being drained


This continues to be debated by so many, but like this person, the debate is meaningless in the face of realities. I'd refer everyone back to @taviso's work up of SMS "2FA". [0]

The amount of 'splaining going on in this discussion helps illustrate the trouble. If SMS2FA were actually fit for purpose it would not require so many internet defenders.

[0] https://blog.cmpxchg8b.com/2020/07/you-dont-need-sms-2fa.htm...


To the OP,

Please don't use cheap providers like Boost. I have done audit and I found Sprint to be superior; however, they got merged with T-Mobile now. Sprint was the best provider that prevented most hijacks.


That's pretty neat, can you describe what you check when auditing a network?

One of the protections enforced in my country is this – for 24 hours after mobile number porting, all incoming/outgoing sms are blocked. And on both the current sim and new sim, notification sms are sent to inform the user that mobile number migration is occurring. This gives you the opportunity to notice and put a stop to it if it was triggered fraudulently. But of course there are corner-cases to this. If you are personally targeted in the meatspace, then all bets are off.

I had to go look for how people might be able to hijack the SMS system. This led to [0], which was discussed on HN about three months ago [1].

Interesting, yet an attacker would have to spend some amount of money per attempt. Unless they are targeting high value individuals this does not seem a likely threat for the average person.

Other methods exist, such as SIM-jacking [2]. I wish the article included a list of phones that might be vulnerable to this attack. Are iPhone's vulnerable?

And yet, while "free" this still requires a massive automated net to be deployed in order to gain some information and then socially engineer your way into gaining access to sites and services that might be of value.

I guess my question is: How common are these attacks? What's the scale of the activity? I have never heard of anyone in my immediate and even extended circles having any such issues. OK, I have indoctrinated most of my family into not clicking links in SMS messages and most of my extended circles are technically savvy. What does this look like in the general population?

[0] https://www.vice.com/en/article/y3g8wb/hacker-got-my-texts-1... [1] https://news.ycombinator.com/item?id=26468892 [2] https://medium.com/auedbaki/how-hackers-hack-phone-using-sms...


As someone advocating against this for a while, who has a internet only sim these days and no phone number it is scary how many companies depend on SMS for security.

Even if it's only second factor today, what really prevents the company from allowing password resets one day? Nothing, I likely would not even notice it until it is to late.

I can own an email address, but I can never own a phone number. Nearly all contracts clearly state that the number is not actually yours in different wordings and nothing prevents anyone from reclaiming the number and give it to someone else.

It's stupid. And annoying.


I had this happen with AT&T. Someone bought a new phone on my account with a phone upgrade, they transferred my service to the new phone, and I had to go through a ton of headache getting them to give me my service back to my old phone and trying to figure out what happened.

At the end, they acknowledged it was fraud. Additionally, added guards on the account with an additional passcode and wording stating that a person must confirm with me specifically before anything like transferring services is done again.

It did however blow my mind that something like that could happen and if someone intended on getting access to my accounts, the situation could have been much worse.


This seems more of an problem when living in the USA than an SMS problem. I'm in Germany and there is no way someone gets a new SIM card without someone checking the persons personal ID.

You can request that your mobile provider put a port freeze and SIM lock on your account and require you to be in-store with a valid photo ID to transfer your number to another device.

https://help.coinbase.com/en/coinbase/privacy-and-security/d...


Yeah but if that's not the default 2 factor authentication is not secure and its an illusion of safety. For companies and groups to claim its gives you all this security when it doesn't follow through even in the default case is misleading. No shade on you but your talking about a lot of hops to go thru just to make someones broken model work.

Having had this almost happen to me, I always strongly recommend that you remove your phone number from Gmail as a recovery method. And then go and test it out to double check.

SMS 2fa is okay but SMS recovery is not okay and high risk.

It's also ideal to have obscure email addresses used for, say, coinbase so that in the data dump they they likely have, containing your email to phone number mapping, points them to the email address not linked to coinbase.


The worst part is, Coinbase will not cover your losses. They have absolved themselves of any responsibly for users being hacked, only if they [coinbase] gets hacked.

Worst part, I mean that’s the majority of the risk of crypto. These aren’t government backed accounts, why would there be insurance.

Since I wasn't sure if this is just what their ToS claim or how it's handled in practice, I googled a bit, and found this case:

https://finance.yahoo.com/news/coinbase-hacked-accounts-get-...

So this indeed seems to be how Coinbase handles it.


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