SMS is not 2FA-secure | Hacker News Reader

SMS is not 2FA-secure

issms2fasecure.com

867 pointssergeant3371 comments

This is great; it's a Princeton research project from Arvind Narayanan's (@random_walker) group, in which their team made 10 attempts to SIM-swap each of 5 different carriers, including T-Mobile, AT&T, and Verizon (all three of which were, weirdly, less secure in some ways than the 2 MVNOs they tested).

Most notably: AT&T and Verizon both use call logs to authenticate SIM swaps from people who don't know the account PIN; requestors are asked to list recently made outbound calls, or in some cases inbound calls. A targeted attacker can trick a customer into making a known call (or, obviously, can simply call the customer to make inbound call records), and then authenticate with them.

AT&T uses billing statement data as a factor. But the research team was able to "spoof" billing statement data by purchasing prepaid refill cards and applying them to a target's account.

The report also identified a bunch of online services for which SMS was used not just as a second factor but, through account recovery, as a sole factor, meaning you're substantially worse off with SMS authentication than you are without it at those services. The reality is probably worse than the report highlights, since a lot of account recovery processes are informal and ad-hoc, and can be socially engineered into relying on SMS.

> account recovery, as a sole factor, meaning you're substantially worse off with SMS authentication than you are without it at those services

But if in those cases you disable SMS auth, then you can't recover your account right? That might be considered worse off in some cases.

What worries me isn’t that I might not be able to recover my account if it uses some other form of authentication, it’s that I might not be able to recover my account because it requires authentication from a phone number I lose access to.

This just happened with my AWS account. Changed phones and forgot to update the number. Didn’t realize it until it was too late. Their recovery process without the phone is incredibly onerous (as it should be) and way too much hassle for me to go through for a small personal account. I just deactivated the credit card that was getting billed and let the account get cancelled. That was a hassle, but not nearly as much as getting back into the account.

And by the time you regain access to the phone number, the account might already be using a different one...

They generally run a cron job on your email to see what are the vulnerable accounts & then decide in order to which one is most important

So how SHOULD this problem be solved? How should account recovery work?

Walk into a store and provide a government ID and the original SIM card. If customer doesn’t have the sim/phone, send a recovery code to the billing address on file in lieu of the SIM card.

> Walk into a store and provide a government ID and the original SIM card.

This is how it works in Poland since September 2019, after some recent SIM-swap attacks. You can swap SIM or get a replacement if stolen only at store showing government ID. It is free of charge with Orange and not always free with T-mobile.

But this has some downsides in real life.

1) I had to walk my 88 yo Mom to the store to swap SIM card.

2) Every clerk at every shop can do that so for a determined criminal it is possible to bribe or threaten one.

3) Virtual operators (MVNOs) usually do not have physical locations and there is a dozen of them.

The problem is that the ID is still checked by the clerk. They could be bribed or tricked by a fake ID.

A recovery code snail-mailed/e-mailed to the account holder when they first open the account is the correct way to go, and if they can't provide it they need to go through a lengthy process where many factors are used to authenticate them (verify their physical address, verify their ID, ask to confirm last call records, billing details, etc).

You can require the clerk to note the document ID to avoid bribery.

On your second point, a determined criminal could always deploy rubber-hose cryptanalysis on a 2-factor authentication scheme, but it's still a significant improvement.

Your first drawback is substantial, though.

> criminal could always deploy rubber-hose cryptanalysis

That would be smart criminal with means. I was thinking more of a hood with fat neck passing $20 to clerk assistant to obtain SIM for $5k fraud.

What if you are abroad? My debit card was recently blocked and I had to wait until I went back, walked in the bank and show my face and ID.

Before you go abroad you could notify your bank. Then in period you declared you are abroad they should lower expectation from "in person and ID" to phone call and other means of verification. After that period you are automatically back to normal security.

That is for example how my debit card works. If I want to use it abroad I have to turn that feature on for whatever time I am abroad.

In Europe you have a telephone PIN codes, you have number generators on the app. There are lots of ways to authenticate yourself. IN Europe you no longer need to tell them whether you're abroad or not; I guess the ML algo's that monitor for fraud are so much better than before that this isn't needed.

I'm going abroad all the time and I'm sure this wouldn't work anyway. Last time I was in their office I realized how backwards they are.

So the bad guy can just notify the bank that you are traveling abroad, and then use the easier method to gain access.

I think we just need to be prepared for these sorts of things. Travel with cash, your debit card, and one or two credit cards. If you can afford it, have a backup SIM (Twilio sells SIM cards for about $3 and the cost to keep them activated is $1/mo, and nothing more if you don't use it [0]). Use a Twilio or Google Voice number that you don't use for anything else for 2FA or account recovery for services that require a phone number (some providers reject these numbers, but many will accept them).

[0] Full disclosure: I work at Twilio and built the first version of the wireless product, so I'm a bit biased.

It's about convenience. 99% of the people will take convenience over security. Changing behaviour is difficult

Cool. What store? Do all services that provide accounts need physical stores now? How do you ensure the store endpoints are trustworthy, and actually checking said IDs and SIMs?

I meant for the services currently relying on SMS for account recovery... for example, how should you recover your gmail account if you lose access?

Use backup verification codes and a recovery email address.

Also, remember the date when you created your Google account. The best way to find that date may be to look at the first email you received in the account.

".. a recovery email address"

This just moves your security issues to another account.. how many layers of recovery email address are you willing to go before hitting the end?

what store for online-only services?

Yes, like my mobile service is provided by a German supermarket chain that has outsourced the operation to somebody else, who run it as a virtual network over somebody else's cell network. The nearest of these supermarkets is hundreds of kilometres away, and the checkout operators are unlikely to be of much help.

Photo ID seems like enough, no?

Problem with a government photo ID, There's no way to verify its authentic besides a visual inspection. I consider them as secure as SMS 2FA. For $200 and someone could get passable ID with your name on it.

That's the key problem that US needs to solve - the businesses don't really have a solid gov't ID system to fall back on. In most of Europe (UK seems to be more like USA as far as I understand) passing on a counterfeit ID to a mobile shop is harder (and more rare) than paying with counterfeit money, the IDs can be checked, employees are required to verify online if that ID has been reported lost or stolen, etc.

I mean, in Europe if criminals want to get a bunch of stuff on credit from some place with a disposable identity, they generally recruit poor/homeless people with real IDs, because that is simpler/cheaper/safer than trying to do it with counterfeit IDs.

SMS hijacking, just as the core identity theft issue is so much rare elsewhere - it demonstrates that it's a solvable issue if the USA wanted to solve it. (in some sense the discussion on identity theft reminds me of https://www.theonion.com/no-way-to-prevent-this-says-only-na...) However, the straightforward way to do that would require a proper single centralized (i.e. federal) gov't ID issued to almost all people, which seems to be anathema in USA.

I’m not in the US, but the only ID card without a chip that I can think of here is a European driving license, which is just a plastic credit-card-sized thing that is often used as informal verification eg to collect a parcel.

Not necessarily, all IDs here in Portugal have a chip that can be used to verify its authenticity.

$200 and greater risk of getting caught -- that's still a step forward. Right now it only takes sitting at home spending a few cents to call customer service and social engineering them.

This is not true everywhere. There are Aadhar cards in India where you can confirm your identity with biometrics at any store using government-provided equipment that many stores have.

My DL has a barcode that can be swiped. They already use it at grocery stores to confirm that you are over 21 and that it's a real ID.

A sim transfer/ account recovery process should come with a transition period of multiple days during which SMSs with warnings are sent to the original sim card.

On top of that, one could think of: A passphrase to authenticate a number transfer to another sim.

Sending a code through physical mail.

I've implemented something like this at Dontport. There are few work arounds but again security isn't something that's on top of traditional carrier because it's a problem with a small set of people

Nice product!

https://dontport.com/

Do you know if something like this exists in europe?

Not yet, but soon we'll launch in Europe too

Apps like Google authenticator, or more conveniently, a Google voice number. The Google voice solution works well since it can't be Sim swapped, and can be accessed via email (admittedly, a potential downside).

Google voice is a US only service.

How do you recover your google voice account if you lose that?

And down the rabbit hole we go...

Long recovery passphrase that you write down and keep in a safe

And if you lose that?

Well first of all using a password manager should be the last resort recovery strategy. Unlike device based 2FA a password manager allows you to make an unlimited number of backups.

After that 2FA should always be device specific. If you want to do 2FA with your phone then the 2FA challenge should not get sent via an identifier like a phone number that may change owners. Instead you should download a 2FA app that generates a private/public key pair where the public key is linked to your account. That way the only thing you need to do is wipe your phone remotely if it gets lost.

A web of trust style arrangement would be interesting, 2/3 of previously named recovery pals would have to verify you.

What about setting up two mobile phone numbers for recipients of the recovery code: 123 sent to phone #1 and 456 sent to phone #2? (Phone #1 is yours and phone #2 is your elected trusted partner’s)

Won’t this work?

Who should single people sign up as #2? Their mom? And what if your SO is currently unavailable?

This is a terrible scheme.

Doesn't have to be SO. It can be a trusted friend who knows in advance that you may voice call them in a password recovery scenario (voice calls not via text).

Edit: regarding the "lack of availability" at the point of wanting to reset the password: the urgency of resetting passwords should be considered a lesser inconvenience than the risk of having lost control of your account through insecure 2FA.

(I am simply supporting my original brain storming thought through ... I am not married to this idea in any way or form. Just a thought.)

Seems straightforward, all these phone companies have endless kiosks and offices. Legislate that a phone number can only be transferred by making a confirmation call to the old phone or in-person with a salesperson who is checking ID.

In Europe, neither of these is viable without a complete overhaul.

- There are online-only providers. E.g. Giffgaff in the UK, Mobile Vikings in Belgium, etc. - Many European countries offer prepaid SIMs that aren't tied to ID. Instead, you can just buy them in the supermarket the same way like you would a gift voucher.

On the contrary, in most European countries, due to anti terror regulations, you now need an ID to buy a SIM card or if you've bought one before this new law came into place you have to send a picture of your ID to the Telecom operator or your sim card gets deactivated.

Not saying I like this or that this is good way forward but it's a reality that contradicts your assumption.

This will do nothing to deter malicious SIM swaps. Someone who's happy to take over your number and then steal your money is also happy to present a fake ID and pretend to be you.

What kind of ID is it? A proper barcoded photo ID that corresponds to a government database? Because with that you can verify that the ID picture matches the one in the government database.

Assuming that ID gets logged in a database accessible to customer service people, it seems like a database check for IDs and IMEIs would be workable as a way to confirm "sorry, we can't port that number to your new SIM card, the ID card registered to its IMEI doesn't match your old phone number's ID card". You could still do it over the phone, then, since an ID was logged against your sim card when you bought it.

People can be bribed and that's the basic flaw

I wish Apple added iMessage as a service to make 2FA more secure.

I wish banks and suchlike would get with the program and use Google Authenticator or equivalent.

Even if iMessage could be a more secure 1.5FA, it would still be 1.5FA and not true 2FA.

After using TOTP like Google Authenticator since around 2013, I now think the friction needed is just too great. Especially for banks which log you out after 15 minutes or so of idleness. Google doesn't do that.

Not to mention Google Authenticator deliberately prevents these stored tokens to be backed up and transferred to a different device, which makes upgrading devices troublesome.

I wish everyone would start using Yubikeys. WebAuthn is now widely supported by browsers.

Why not use an open TOTP app like AndOTP. I use it all the time for sites that claim to require Google Authenticator, it works, and its easy to backup the secrets as plain text or encrypted with a password. I keep it current on my primary phone and a cheap offline backup, in addition to backing up the encrypted secrets file.

People recommend Authy. As far as I can tell they rely on cloud sync/backup like any other app in that space.

Isn’t google authenticator not using this on purpose? Central account and sync is googles thing and yet they deem it too insecure. Completely understandable

So how can using a central service that adds yet another attack vector be of value?

What I would love to have is a paper export. Every time you add a new account to google authenticator you can print it as QR code for later reimport.

Yes many services already provide this for you via recovery codes but having it on a per service basis directly from authenticator is probably much easier to use and not less secure

Any reason this wouldn’t work?

Don’t put them in google authenticator.

https://support.1password.com/one-time-passwords/

Isn't that solvable by not requiring 2fa for "registered" devices?

> Not to mention Google Authenticator deliberately prevents these stored tokens to be backed up and transferred to a different device, which makes upgrading devices troublesome.

It doesn't offer export in the app UI. It's not doing anything to prevent you from backing up the tokens yourself; they're stored in the clear in the sqlite database for the app.

If that's too much for you, there's a good chance https://github.com/puddly/android-otp-extractor can get them automatically.

Use Authy instead of Google Authenticator. Problem solved. RFC 4226 doesn't specify that you can't have shared devices.

Use Authy. Can be transferred to a new device.

>Not to mention Google Authenticator deliberately prevents these stored tokens to be backed up and transferred to a different device, which makes upgrading devices troublesome.

If that were possible then you would face the same problems that reused SMS numbers suffer from.

AFAIK, in the EU all banks are required to have "strong authentication" which usually means using 2FA via biometric authentication on your phone.

Classic Google Authenticator does not seem much more friction than that.

WebAuthn is definitely the way to go. The security key approach is such a better user experience that the app based approaches.

What absolutely confuses me is.. aren't TOTP authenticators like the cheapest 2FA option to begin with?? No need to have some fancy SMS Enterprise account with a Telecom or pay okta or duo or entrust a bunch of money. It's FREE, all you have to do is implement the server side which is very straightforward.

My banking app requires a pin (or fingerprint) to read data, and a password to make transactions.

The website requires a temporary code, generated by a card reader and my card. It works like a 2FA code, as I need to _have_ my card and to _know_ its pin.

In Norway most banks have been using 2FA for 15 years or more I think.

Recently however it has become somewhat less strict it feels[0] and I can now log in to my bank app using FaceID or a pin code.

Normal bank websites still demand a code from a hardware token (think RSA key, but with a pincode and sequence-based instead of time based.)

[0]: I realize it might be that they are just as strict only doing more work in background to verify me instead of bugging me.

My bank does. The iPhone app can generate tokens. I get the feeling that US retail banking is way behind Europe.

My brain isn't working right now... Can you tell me why something like google authenticator could not be executed as a website? Does it have to be an app?

Just wondering if there could be an easier non installed version that was always available.

Apologies if it's a really silly question!

I could see Apple offering 2FA as a core feature, at least on iOS.

In fact, Apple should redesign Keychain into a user friendly, 1Password-lite product with 2FA built-in (1Password offers this too) or as a separate app that works with Keychain.

iCloud Keychain is already a better-than-1Password 1Password-lite and 2FA itself for your Apple id is built into iOS and macOS. I think the limiting thing there is desktop Safari - you don't really notice the full integration unless you're using Safari on macOS as well.

Apple has had mandatory device-based 2FA for a while now, but it only works for iCloud logins.

Isn't iMessage just as vulnerable to SIM swapping and number portability fraud as SMS?

Once you have control over a phone number, you can register iMessage as that number on a device you control.

It depends. If your iMessage account is tied to an Apple ID used on multiple devices with 2FA enabled then the code is sent to one of those other devices to validate the login on the new device. So if you are fully in the Apple ecosystem and have 2FA enabled then I believe it would be secure. I know I get alerts on my other devices any time I have had to re-add my phone number to an Apple ID. It tells me my phone number is now being used on another device. So at the very least you would probably be notified.

When you get the prompt to input the code, just choose "Did not get a verification code" and it will fall back to SMS.

See: https://blog.elcomsoft.com/wp-content/uploads/2016/03/apple_...

iMessage is only tied to an Apple ID for the e-mail part (where they can send iMessage to your e-mail). The phone number part is independent of that and you can take it over provided you prove ownership of the phone number (by inserting the SIM into an iPhone, it'll send an invisible SMS to Apple and back and that then activates iMessage on that number on that new device).

Apple accounts in general also have mandatory SMS 2FA if 2FA is enabled.

Isn't there a registration step for new SIMs with iMessage?

I think there’s an SMS sent without any visual indication and without asking for explicit permission (or I missed it if there was a tiny text warning). I noticed it when I saw an SMS, in my bill, sent to a Singapore number which, as an international SMS, was changeable (SMS is mostly free here).

Why the downvoting? iMessage is a hundred times more secure than SMS. It’s got E2E encryption and a published security paper.

https://techcrunch.com/2014/02/27/apple-explains-exactly-how...

Unclear.

iMessage still depends on verifying your ownership of a phone number and can be taken over with a SIM swap attack.

My understanding is that you don't even need to do a SIM swap, because the SS7 signaling system is insecure. SIM Swap is likely the easiest way as wage-slave employees are quite pliable to bribes[0]. But if you want to be even more anonymous, you can apparently re-route texts remotely [1].

0: https://www.nbcbayarea.com/news/local/mans-1m-life-savings-s...

1: https://www.kaspersky.com/blog/ss7-hacked/25529/

I thought both these vectors were already common knowledge to HN readers.

> I thought both these vectors were already common knowledge to HN readers.

One person can't know everything... that's why I come here. Thanks for the info!

Yep, the security problems with the mobile system are ghastly.

- Stingrays...

- Operator app pushes to SIM cards...

- Secret GSM processors and software internals

- Voice / text / data "ciphering"

- Protocol-level "emergency" tracking features

- Silent SMS (sounds like its from a bad cop show but its actually a real thing it turns out.) "They do not show up on a display, nor trigger any acoustical signal when received. Their primary purpose was to deliver special services of the network operator to any cell phone." -- sounds like it has a completely legit use...

The list goes on. It's enough to make anyone want to get the tin foil out. But at least in this case there's a simple and clear recommendation: --not to use 2-factor auth by SIM--.

> sounds like it has a completely legit use...

The original purpose of silent SMS was to send voicemail or missed call notifications to handsets, which would trigger an icon to be displayed on the device. Sending a regular SMS would be annoying as the user would have to delete it - after you've listened to your voicemail, another silent SMS can be sent to turn off the notification. Also originally SMS was stored in the SIM itself which had limited memory, so it would be not be very convenient if you didn't receive a voicemail message as your SIM was full. Remember this is a 28 year old feature of GSM.

The tracking argument seems somewhat mute, maybe when this first came to light 10 years ago it wasn't the case, but nowadays I would be very surprised if operators do not keep detailed logs of all the IMEI (unique identifier for a given device) and IMSI (same, but for the SIM) that connect to their towers.

The SIM Swap would seem to be a bit more accessible to the average fraudster. Hacking SS7 apparently requires setting up a "hub" and obtaining a carrier license from a lax country. That is, until we get to the bit about "illicit merchants offering ‘Connection-as-a-Service’ to such hubs."

https://www.kaspersky.com/blog/hacking-cellular-networks/106...

> obtaining a carrier license from a lax country

Carrier license sounds much more involved than what it is. It's not uncommon to sell full SS7 access to companies that are not operators in the regular sense.

>SS7 signaling system is insecure

If people knew how telcom (and the internet) was held together with bubblegun and duct tape...

Multiple proposed fixes and replacements to SS7, to the best of my knowledge none of them are going anywhere. And even if it was pushed hard, it has to be a global thing.

Governments and the security industrial complex do not want it fixed. Vulnerabilities in SS7 are features to exploit, not bugs.

More than that it's the amount of work and cost. Average consumer doesn't care about it so why fix something that's not broken. People won't pay more for it

I am pretty sure this is how they got Bezos' texts. All you need to do is register a CLEC and then you can get your official hookup to SS7. My experience isn't with messaging but I'd imagine if you bid* to deliver messages to a certain area much lower than other carriers, you can target people.

* Bidding doesn't happen in real time, but you can tell carriers your "rates" so to speak.

I'm just amazed he was stupid enough to not understand that his texts, messages and devices are compromised.

In the future, the term SIM Swap will likely be replaced with something like "SIM identity theft" so that banks and telecoms are not liable. Then we can all buy SIM identity protection.

Does that mean an authoritarian government can read the location and sms of a number from foreign country without any cooperation from the carrier?

Scary thought

Doesn't have to be government but any one

Not in Russia. Numerous examples exist when victim's number was linked to attacker's sim card to obtain 2FA code, then linked back to victim's sim so he does not notice anything.

This happened both by government-linked parties, where they are able to coerce providers to do it, mostly targeting prominent political opposition members. It also happened without government involvement, done by provider's personnel with sufficient access and some entrepreneur attitude.

The rule of thumb to protect against it:

- do not use SMS 2FA

- if you do, use a foreign SIP number with SMS capabilities

- if you HAVE to use local sim, use SIM that belongs to someone else and noone knows you use it

Just google for "форум пробив" and you will find black market for accessing any kind of information, including SMS, phone location, etc and associated services for hacking accounts (VK, Gmail, etc). You don't need to be a government, it is open for everyone.

That type of service can allow the attackers to access SMS contents, but not from swapping numbers back and forth between SIM cards. And without it, the victim will know he is being attacked.

It's also important to know your threat model. Namely, random attacks versus targeted attacks.

Shitty 2fa will still deter people who get a list of a hundred million emails/usernames and passwords and try them on banks, Twitter etc from putting in the extra work to break into your account specifically.

If you expect targeted attacks - from governments, because you oppose them, from determined criminals, because you have a lot of nice stuff to steal, or from people around you, because you know too many assholes - maybe it might as well not exist, but for most people, most of the time, any 2fa is better than none.

> if you do, use a foreign SIP number with SMS capabilities

Any good providers? I've tried Twilio SMS forwarding, but different services (e.g. Steam) reject it for 2FA since they're pretty much considered throwaway numbers, I suppose there's some sort of blacklist

For UK numbers lookup Andrews & Arnold. They have mobile numbers from a national carrier's numbers block so no way for them to be flagged as VoIP. They work fine with both calls & SMS.

I've had a lot of luck with Voip.ms as a provider for short-codes. Their wiki states that they cannot guarantee they work (which I take no surprise in), but I don't recall having one fail since they rolled it out. I've used it for Signal, Whatsapp, and more that I'm sure I've forgotten. Even better, SMS is forwarded to email - available from my desktop or phone.

I have used zadarma.com, they are very cheap and have an app for Android that works rather well

I want my things protected by a human with a process to unlock/reset/.. given some kind of proof of identity.

Because with 99.99% certainty the person that needs to unlock the account is me, and not an attacker.

Even with a dozen backup yubikeys and spare codes written down I’d still be much more likely to lock myself out than be attacked.

If it’s one thing I have learned the hard way it’s that the most dangerous person in the equation is myself. I won’t trust myself with any kind of security.

> I want my things protected by a human with a process to unlock/reset/.. given some kind of proof of identity.

Anytime you have a human in the loop you have the risk of human failings. I.e., that human forgets to follow critical step X in the protocol. Or that human falls for the attackers emotional sob story and takes pity on the attacker and lets the attacker unlock your account. Or that particular human is amenable to bribery to obtain the outcome the attacker wants.

In fact, many sim swaps have been reported to have occurred because of "human at cell phone store did not follow protocol" or "human at cell phone store was taking bribes".

So having a human in the loop is not an absolute solution to solving the problem.

> Anytime you have a human in the loop you have the risk of human failings. I.e., that human forgets to follow critical step X in the protocol

This is exactly my point. If the risk of an attack is X, the risk of me being that person who fails or forgets a critical step of the protocol (backup yubikey, whatever) is a hundred times higher. So this system of “flawed humans interacting” to me looks like the lesser evil.

I don’t want my things protected by foolproof protocols. I‘m the fool you see.

Bingo. This is why crypto currency won't take off without more humane tech being inserted into the process. People aren't robots. We want many many ways to un-screw ourselves when we inevitably screw ourselves.

That's why I'm bullish on things like Shamir's Secret Sharing and other social recovery tools.

It's an iron rule that the more automation, the more important are the humans that remain.

I'm not sure you get this. Google hasn't seemed to get this in the past. They have added some customer support though.

That's how https://jmp.chat/ works, and you can make your phone number as arbitrarily secure as you want with JMP.

Any port-out requests are handled manually - you are contacted by a human to ensure that you made the request. You can ask them to put a verification code on file for you to confirm when this happens if you're concerned about the security of your XMPP account (which itself could use whatever kind of authentication scheme you like).

Good luck trying to use VOIP numbers with US banks these days

In practice it seems to work fine with the banks I've tried. There may be one or two that don't accept numbers whose type is listed as "voip", but they are in the minority.

There is also work being done to update the type field of JMP numbers so they appear as "mobile" instead.

Yup, I have the same misgivings. I hate getting locked out, but at the same time, I'm pretty paranoid and want secure passwords, don't leave copies of them around.

So I've been working on a backup plan. Current incarnation is to use a simple Go cli tool with Shamir's secret sharing algo to break a password into N/M shards. The user can then do whatever they please with the shards, give some to their family, friends, attorney, make a pirate map, get an rfid chip, anything you want.

This would be a nice solution for giving your family access after death too.

They can meet at the funeral to assemble your horcruxes.

Even with a dozen backup yubikeys and spare codes written down I’d still be much more likely to lock myself out than be attacked.

I am not sure this is true. Most people regularly get phishing e-mails and apparently fall for it.

SMS and TOTP (due to the window of time the TOTP code is valid) only provide limited protection against active phishing attacks, since phishing site can 'proxy' the the SMS/TOTP code besides the password.

I think I would prefer losing access to an account (since I make backups of critical stuff anyway) than my account getting compromised, which could lead to identity theft/fraud, etc.

My ideal solution for an ultimate reset/unlock solution would be to show up and have my DNA sampled. Impossible for me to lose the reset key there, and with appropriate DNA extraction procedures, it is nearly impossible to spoof.

The issue with using permanent characteristics for auth is that you lose the ability to revoke one credential in favor of another.

That's not a problem if you have to physically show up though, since no one can spoof that.

As another person said, you're literally leaving it everywhere you go.

If you need a blood sample, then would donating blood be considered compromising security?

Identity is what your DNA is. Password is a secret. Your DNA is not a secret.

That's exactly what they did in the movie Gattica- it's hard but seems totally possible. I'd rather have multiple revokable keys.

Your DNA can show up all over the place.

>with appropriate DNA extraction procedures

Carriers have already demonstrated their complete across the board failure to have appropriate security procedures. Your DNA isn't hard to find, you leave it literally everywhere you go.

And do you really want mobile carriers creating a DNA database of their every customer? The same companies that already sell your location data to bounty hunters?

That's going to be a big no thank you from me.

While I basically agree, why do you think they'd need your actual DNA? Wouldn't it be hashed?

Consider identical twins, mothers, and organ donation or blood transfusion recipients.

This is where countries like India are going with Biometric Auth plus 2FA (though the implementation has issues). The government provides a public API for sending fingerprint or Iris scan data plus SMS 2FA to authenticate identity with a cost.

Worth noting that this is just for US and for prepaid SIMs, from their paper “We examined the types of authentication mechanisms in place for such requests at 5 U.S. prepaid carriers—–AT&T, T-Mobile, Tracfone, US Mobile, and Verizon Wireless”.

It doesn’t mean that for the rest of the world SMS 2FA is completely secure, it’s just a lot more difficult (or impractical/impossible) to do a SIM swap so easily. As mentioned in another comment below, SS7 vulnerabilities are another attack vector, globally available and without requiring a SIM swap.

These 5 carriers were studied, but where's the evidence that any other carrier is any better (or that you're any better off as a post paid customer of AT&T, T-Mobile or Verizon)?

MetroPCS (prepaid MVNO now something like a subsidiary of TMo) required the 8-digit PIN on the account in order to change IMEIs. A bot would take down all the info, then if/when it was to a phone you'd never used on their network before, you got put on hold to wait to talk to a human and provide your PIN and new IMEI all over again. Then you'd hang up, power off, and move your SIM. But that was ~18 months ago, before it became "Metro by T-Mobile", so I don't know.

The rest of the developed world is using a same way to verify a person - by providing your document. ID card or passport.

I thought this was going to be one of the otherwise-plaintext black and white web pages with <h1>NO.</> centered in the middle, but interestingly it's actual research, and a nice read (even if nothing new) at that.

If it's nothing new then why do people keep saying it's better to have SMS 2FA then to not have it. The research says "websites should eliminate SMS based MFA altogether".

The answer is no, but is it more secure than no 2FA?

Of course there are much better 2FA options, but for the general public, they are probably too complicated to use.

Everyone understands SMS.

Have you seen the prompt system, as used by Google, Micosoft, Okta, et al.?

In my strictly personal opinion, responding to a notification that asks if a login attempt is you is clear enough that people need minimal training to make use of it. This might just be me, though.

In my career, I've definitely seen people actively choose SMS over other factors on offer. It was easier for them, and in many cases shouldn't have been offered. Your point about SMS being better than nothing is wise and true and insightful, but it's perhaps not always the question as faced in practice.

They (and similar corporate 2FA solutions like PingID and similar systems used by banks) basically assume uninterrupted access to the internet which is generally a poor assumption. It often breaks down when you're traveling either due to network or roaming issues just when you desperately need access.

In all these situations, I've found companies which offer a back up SMS option very valuable since it usually gets delivered.

I'm pretty sure the Microsoft authenticator has a backup TOTP token you can have it display if you have issues receiving the notification. It is quite a user friendly auth scheme, at least I've never had to resort to any kind of SMS backed auth.

In my opinion, that sounds like precisely the sort of system that should not offer an SMS fallback unless the goal is to create a false sense of security in the user. But YMMV, I don't generally need to access my online banking applications when I don't have useful internet access.

I tend to use TOTP for systems where I'm concerned about offline usage. But again, YMMV.

Yeah, and my local walmart has a section where there is no network coverage; I was browsing the store and wanted to check something on my bank app; it prompted me for SMS code, which I didn't receive because of no network; & I would not have received the Google prompt if I needed one for the same reason.

HOTP-based 2FA systems (like Google Authenticator) do not require internet connections.

The problem there is that it's not very clear that you didn't trigger the login yourself.

It's been my experience that it's often reasonably clear to users that they did perform a login themselves in the past few seconds. Adding an approximate location and a short verification token to the prompt generally helps.

Your experience and standards of clarity may be different from mine, obviously.

I think at some point goolge used SMS 2FA as a sole factor in account recovery. So there, you really were worse off with SMS 2FA enabled.

This is really a criticism that Google called their system 2FA but actually was using it as a sole factor. That's bad security and bad naming. Had they actually used it as a second factor, then you would have seen a security benefit.

Well if that's the case they could still offer true MFA. Make at least SMS 2FA mandatory but offer OTP/token based MFA.

Obviously banks are a place with a lot of low-value targets and a few very high-value targets, but the cost to implement MFA is the same so they might as well do it.

Yeah, the by far biggest cost of 2FA is the recovery process which you need anyway, not actual 2FA implementation.

Awareness may make providers more willing to switch to a better 2FA, such as TOTP.

Sadly, providers seem to be going the other way. I had a service try to bully me into disabling TOTP in favor of SMS 2FA this week.

Because they want your phone number. They are more and more used to link to identities, as people tend to keep (and port) their phone number

Hint: if a store ask for a phone number to get a discount, try the local areacode then 634 5789. This is from an old song, and many people seem to have created "anonymous" account with it!

https://en.wikipedia.org/wiki/634-5789_(Soulsville,_U.S.A.)

In Switzerland, we have Mobile ID: https://www.mobileid.ch/en

It uses the SIM to implement a challenge-response mechanism where a PIN is prompted by your phone. While not perfect, it's vastly better than using SMS, without being less convenient.

I don't know if other places leverage the fact that SIMs are smart cards which are perfectly able to perform this kind of stuff given the proper infrastructure.

In India,

if you get a SIM replaced after providing proofs of identity, residence and biometrics, it would get activated after few hours.

The kicker is that it wont get SMSes for 24 hours after the SIM is activated.

In the US, won't it be cheaper as well as secure to get a virtual phone number from Twilio for purposes of two factor authentication? (In India, there is no service at the rate what Twilio offers, but there are some which charge around $30-$40/month for virtual phone numbers with incoming SMSes)

Airtel also makes you to accept that SIM Swap request on old sim if you are not coming in person to a store with ID documents; most of which is Adhaar number verification.

How does this work?

Presumably there's an applet in the SIM card that holds a key pair and allows you to sign stuff by providing the SIM PIN. You interact with it via STK which is an old standard allowing SIMs to tell the phone to draw rudimentary UIs and ask the user for input.

I'm not aware of the details, but I imagine something very similar to EMV payments.

The only difference is that you need to register your SIM with the service beforehand, using a reasonably secure process. Banks make you use their own MFA before you can enable Mobile ID (and no, it's never over SMS).

Protip: security is not black and white

The word "secure" is not binary.

sms as a 2fa is secure.

Just not as secure as a authy totp account

...which is not as secure as a unclonable totp system

...which is not as secure as a hardware token based otp system

...which is not as secure as a hardware token that also requires you enter a pin and a fingerprint to activate it and only communicates using hard coded encrypted messages with the legit service that issued it.

To defeat the Authy account recovery process, you need to perform an active SMS attack (SIM swap, etc) and then prevent the target from seeing the recovery warning emails for 24 hours. Therefore, Authy customers should only tell trusted people that they are going on a weekend off-the-grid camping trip.

The big benefit of SMS for the website is that it outsources the problem of lost 2FA tokens. What happens if the user loses a yubikey. Or changes phones and did not back up their TOTP. With SMS authentication, even if the user loses a phone, they can go down to the local cell phone store and get a new phone on their number and be back in business without the website having to get involved.

> What happens if the user loses a yubikey.

Always buy two. ;-)

Joking aside, I've moved almost every 2FA to hard token, soft-token, or google voice. But the root of trust is still LastPass & Google. I don't see an easy way out of dependency other than power of attorney. Even worse: I worry what happens to my protected assets as I age and possibly face memory loss.

Bad idea: google will disable your google voice after some time of not logging in.

I got bitten in a bad way!

Hopefully twilio will start creating "recognized" numbers someday, as my twilio number is unusable for TOTP. There seems to be a blacklist of all twilio voip numbers.

Interesting! I generally check it once a week. Any idea what their timeout is?

Backup access in a bank safety deposit box is what I do.

I read an article here some time ago that banks take no responsibility if they lose/destroy the contents of their boxes as someone learnt the hard way with precious family possessions.

Right that's why you should verify your backups every year.

No place you store your backup can guarantee it won't be lost or destroyed.

Having either a second yubikey or a totp app as a back up is a wise thing to have. Seriously.

github & gitlab require you to register a TOTP authenticator app before you can enable U2F (presumably to avoid manual resets, although they don't say)

google's enhanced protection requires you to have 2 distinct yubikeys to sign up

Double-edged sword.

Your website is outsourcing security to any company which can service a cell phone account, which may be better than your website security or worse.

I know that google branded “titan” yubikeys come in pairs. One is for keeping in a safe place for recovery.

The title is mangled, because someone misparsed the question.

The question is "Is SMS 2FA secure?", not "Is SMS 2FA-secure?" There is no such property as 2FA-secure.

Title should read: "SMS 2FA is not secure".

I agree. "SMS is not 2FA-secure" implies SMS is not suitable for 2FA at all. In reality, SMS 2FA is still very valuable to most people, even though it's not secure enough.

But how else are you supposed to encourage users to give you their phone numbers so you can track them better?

No company would ever do that, right? Especially a social media company. Clearly there would be public outrage and their stock would plummet.

For anyone who doesn't detect the sarcasm or is unfamiliar: https://techcrunch.com/2018/09/27/yes-facebook-is-using-your...

Just use a token like yubikey. I have a small fleet and am very happy with the decision.

The only problem is there are very few services that get it right. Get it right means support multiple tokens and allow to truly disable any other means of logging in or recovering the password.

Most services seem bent on allowing many ways of logging in without giving a choice. For example, they will advertise they use 2fa tokens but then if you can't produce one they will still allow you to log in with SMS or mail (ie. password recovery by mail). Facebook will not even let you set up tokens without having SMS set up as a factor and the phone number verified.

I hope slowly developers will get more aware and they will be better tooling (and stack exchange answers to ctrl+c ctrl+v...) to do it correctly.

What about Authenticator? Maintaining a small fleet of yubikeys costs as much as a whole phone.

https://play.google.com/store/apps/details?id=com.google.and...

Know that if your single phone dies with all your totp credentials, you're sunk.

True, and this is the reason I instead direct friends to options such as Authy or Aegis which allow the use of more than one device.

Unfortunately my bank (ANZ) and my government's online platform (myGov) in AU both have dedicated OTP apps which only allow single-device installations. When I lived overseas, my bank in Germany also had their own dedicated OTP app but they allowed installation on a backup device as well. Much better.

Only if they neglected to offer backup codes (which anyone who does TOTP should).

Otherwise, you can just grab a few backup codes out of your fireproof safe and register your new totp code, or go to the bank and get them out of your bank vault.

Sure, the fireproof safe costs as much as a few yubikeys, but if you go the yubikey route you both need the yubikeys and a fireproof safe and bank vault for your spare yubikeys too.

Fireproof safe? Just use a text file and encrypt it.

Or a password manager file only for TOTP backups.

Don't use text file. Use regular piece of paper, put it in tamper-evident envelope and keep register with events regarding envelopes.

When you take something from envelope, note the date, the why, the number of envelope you opened and the number of envelope you then put the piece of paper in. Every time you open envelope check with the register that the numbers agree.

And yet my bank (Chase) only supports email and sms 2fa with no option for OTP/TOTP. Is this just a institution dragging their feet or are there more regulatory reasons why they won't allow more secure authentication?

At least they offer codes via email. I can (and do) secure access to my email account and domain registration with a very long password and a Yubikey. That’s “good enough” for my purposes.

"secure" and "email" really do not belong in the same sentence.

Most email is unencrypted during transit, so a state level adversary can still easily intercept it. For most people this is however sufficient.

Absolutely, a state-level opponent could get up to some shenanigans though I would argue that a state has much easier methods to go cracking into my Visa card. My threat model doesn’t include nation states targeting me specifically because, simply, if one comes after me I am screwed anyway.

As for email being unencrypted, I think most of it now is encrypted during transit (thanks to the Big Two providers knocking points off a spam score if a message does come via TLS) and even if it weren’t the password is also not known so the second factor is not useful. For example, I just tried to log in to chase.com and the code they emailed me at 1752 MST is 067315.

If I’ve been phished so hard that posting this is useful, again I’m screwed.

You hardly need to be "state-level" to spoof bgp or dns.

I asked them over twitter back in may.

https://twitter.com/skunkworker/status/1131297869703438337

For anyone who wants a US bank with TOTP, schwab works! I was pleasantly surprised to discover this. It uses some symantec stuff (as did paypal earlier), but it's TOTP underneath and can be used with any TOTP app.

There is even a "Use Token" button on the Chase login page, but apparently only business accounts can use it.

at least one of my banks cannot SMS me codes, I can't remmeber which, so I always forget, try it, and have to select another method.

I THINK it's chase, but I'm not sure.

They have my correct phone number, but for years now, the code just... never shows up.

Are you using Google Voice? I have the same problem with Chase on my GV number. Calling works fine, and so does email, but no SMS.

Port a number to GV, it will work, but you are at risk of losing it if you don't log in often enough. I lost an important number that way (along with my grand fathered free google apps account for my domain)

I have few personal google apps grandfathered account, & I think it sends an email to all admins if you do not log into it for about 10 months.

It’s more to make customers feel better than for security.

Is SMS 2FA Secure? No, I agree.

Is SMS 2FA enough for most of the people today? Yes

Is SMS a cost-benefit solution for most uses? Yes

Is offering or forcing SMS 2FA and not offering an option for only TOTP asinine? Yes.

It’s free, and requires a tiny bit of additional configuration to enable. No reason not to offer it.

In a previous company, one of the employees enabled 2FA for their staff account (it was mandatory), stored the backup codes on his phone (presumably as a photo) and it fall in the ocean the next day.

With large enough numbers, you'll see everything, but you don't even need large numbers to get people whose lives are made more difficult by technology.

Yes, that is exactly what I want. Life should be much more difficult without the TOTP and backup codes, so much that it takes a great deal of resources to get around it, if at all possible. Maybe even providing heavy documentation such as a Facetime call with various proof so that fraudulent actors are sufficiently deterred.

Dude. If somebody wants into your account specifically, they’ll get into it. 2FA, specifically SMS based 2FA, is really about the provider getting mass compromised because people recycle their password across all their sites.

It great for keeping people using scripted attacks against a huge list of accounts. It isn’t really to keep people specifically after your account out.

If somebody wants your shit and specifically your shit.... they’ll get it...

In a previous job I implemented a recovery page with a long random key (also posted as a QR code) that you could print out and use as an emergency password reset if ever required. You'd scan the QR code and it would take you to a page where you could set a new password directly.

This, coupled with a "I know what I'm doing, never let support reset my password" option that disabled changing the user's password for anyone without direct write access to the production database was pretty good for security, I feel.

There is a reason for that, most average Joes just can't handle the technology. You can change OTP-SMS in Banks for TOTP, but it involves more complexity and probably it will be more prone to user errors.

Configuring the seed, remembering an extra password to use the OTP... For me it's not that hard, but probably my mom will need some help in order to remember all the steps...

So make it a non default option? No one who doesn’t want to use TOTP would even have to know about it.

I know some services require SMS in order to force collection of user’s phone number, for data selling purposes and to prevent bots.

DontPort.Com - I built this to fix this. I've been a victim of this 4 times and was too much frustrated. Unfortunately Sim swap is only one way to get your 2FA but the risks are much higher which I am working to solve one by one

Which common cases does the insurance cover? What uncommon cases does it not?

How do you protect against an insider attack?

This is very interesting. Do you have a third party security evaluation that you can share?

You know what's funny? LinkedIn is supposed to be a 'professional' social network (Microsoft owned) and a friend of mine was asked to add a phone number 'For security purposes'. I knew this was suspiciously involving 2FA SMS + a bonus of spam callers and I told him to press "Not Now". Whilst the world is moving to U2F and time-sensitive codes, a security system using SMS 2FA is now equivalent to a single PC running Windows XP in a bank.

But its not just LinkedIn. Its a huge list of major companies including some FAANG ones too. Oh dear.

Not true. Not true by far. That's an over statement. 2FA is only one of two factors, you need the the password, you need the mobile number and you need to obtain a duplicate or being close to your victim.

You should be worried if you are a POI or you are being targeted personally. And if it is so, SIM Swapping it's just one option and if it doesn't work there are other methods (breaking in, stealing yubikeys, mobiles...)

You don’t always know if you are a target.

LinkedIn is absolute scum in that regard. They pestered me for my number for ages until eventually they finally implemented TOTP 2FA which I then enabled.

They still ask for a phone number when applying to jobs through their platform. I always put zeros or random digits in the field and put the real one in the resume.

All of this happens because we've outsourced digital identity to the telecom companies. Telecom companies are not competent at establishing identity. It's not their job. There is only one entity that is the real root provider of identity and that is the government.

We are never going to get the benefits of digital identity until the government wakes up and brings its services into the digital age.

No, it isn't at all. Moreover, sim swap is not necessary at all.

Anybody with direct access to SS7 can send a fake roaming request for your sim card.

Definitely not. In my home country the banks use SMS 2FA.

It's a complete shitshow. Occasionally syndicates manage to get both sides of 2FA lined up (insiders) and clean out someone's account.

Then the bank says not my problem - you didn't keep your password safe. And the cell provider says not my problem - not intended as security mechanism. Leaving the customer poor and sht out of luck.

Want to point to the Google blog article about the effectiveness of different 2FA techniques. SMS is between 76% targeted -100% autoamted bot effective.

https://security.googleblog.com/2019/05/new-research-how-eff...

I don't really trust Authy being used as much as I think anyone else would. For the sites that I have used it with, an Authy account, or just the app is not required. Therefore codes are just sent over plain SMS.

Consider this scenario. Twitch now enforces the use of all accounts that want to stream all require the use of 2FA, after the whole artifact fiasco. Anyone over the age of 13 is able to do this. I don't expect everyone at this age to have a phone number, and I assume these people would rely on their parents phone to pass this.

As authy is completely optional, people may choose to not require another app for their account, in effort of just quickly jumping through another hoop blocking them from going live, or the device owner not wanting to have an app installed.

It just feels weird knowing that this can be a point of failure for a service that solely relies on a single 2FA method that could from an attack like this down to the individual and how they operate.

I'm surprised more websites aren't taking advantage of TouchId. It's so easy for people to use.

Even login.gov supports it!

https://www.slashgear.com/chrome-is-adding-touch-id-and-fing...

Touch ID and other biometrics are enforced locally.

The device is first enrolled, the website gives the device a secret value which the device can put in its secure element. When needing to authenticate again the device checks biometrics locally and if correct then the secure element releases the secret value which is then either passed onto the website or used as part of a challenge-response authentication.

This means if you lose or reset your device you can't get back in despite having the right biometrics.

Yes, that's a security feature. It's also true for Google Authenticator, by design. You cannot officially back up/share codes because of the potential vulnerabilities that a backup would open up.

Yubikey has the same problem you describe. If your key stops working, you'd also be locked out. Yubikeys can spontaneously stop working in my experience.

To mitigate this, sites like login.gov allow you to add multiple devices, so you can have it on e.g. your laptop and your phone, and yubikeys if you'd like. I generally do all three for important sites (or multiple Yubikey when touchID is not offered).

Anyway, my point is that offering TouchID makes a more secure 2FA very, very convenient for the average person. I'm just surprised more developers haven't offered it even though it's been in Chrome for a couple years.

While I like the principle of using WebAuthn, I'm a bit suspect of biometric based authentication.

And then there was this... https://www.vice.com/en_us/article/5dmbjx/how-hackers-are-br...

This post [1] makes a very good point...

Using a few old Google accounts, I experimented with Google’s account recovery options and discovered that if a Google account does not have a backup phone number associated with it, Google requires you to have access to the recovery email account OR know the security questions in order to take over an account. However, if a backup phone number is on the account, Google allows you to type in a code from an SMS to the device in lieu of any other information.

[1] https://tech.vijayp.ca/adding-a-phone-number-to-your-google-...

In many European countries SIM cards are actually locked to a number.

If you change your SIM card you'll have to reset your 2FA setup on the banks site. It's done on the carrier side.

I still hate it tho, as you are locked to a phone number and it sucks when you move countries a lot.

This relies on carrier cooperation. Given they are the ones that caused this shit-show in the first place I wouldn't trust them to make it right. An insider capable of SIM-swaps would also be able to override this mechanism.

The sad part about all of this is the complexity of the new solutions. Webauthn is strong but fiendishly complex. How did we get here?

Websites used weak hashes (md5 and sha1... efficient to compute and attack) to store passwords and allowed users to set short, weak passwords (12345, letmein).

Long passwords randomly generated by password managers and stored as strong hashes (Argon2id) by websites are secure, not guessable and even difficult/expensive to attack offline when the database is dumped.

This approach is simple and easily understood by everyone involved (users and site admins) and would be suitable for the security of 99% of websites. Leaving 'Account Recovery' as the only remaining challenge.

It's really too bad nobody tests Google Fi. I wonder if they would hold up better?

This research doesn't seem complete; particularly the use of a phone number for authentication, that isn't SMS.

Facebook Messenger uses a phone number either tied to your Facebook Account, or identified as the phone number on your mobile device, to immediately log you into a Messenger account, with zero authentication. They literally ask you "Is this your account?" and you just click "Yes" and you are in that account. Even if it's not yours.

If you use prepaid phone numbers, or link one to your account, you can often get into Facebook Messenger accounts that aren't yours.

The odd thing about SMS 2FA is the amount of critical services that rely on it as the only method of extra protection.

You want your: bank, utility provider, entity-that-has-lots-of-personal-data-on-you to offer other secure options.

This might be a costing issue though. When your customers number in the millions, your call center is probably handling thousands of "im locked out" issues per day and these need to be handled in x-minutes. Other security options might cause the time meant to handle these scenarios to increase and SMS is generally 'simple' compared to them.

The only good solution at this point is to legislate cell carriers to make SMS more secure. Everyone perceives it as secure, everything uses it for auth, and it aught to be secure for its own sake.

The problem here is not SMS itself, but that it's trivial to socially engineer most operators into transferring somebody else's number to you.

(FWIW, SMS is also insecure in that it's fairly easy to passively snoop on SMS comms, but that's a separate problem.)

In Turkey if you change your SIM card your bank is notified and you cannot login to your bank account. You have to re-validate yourself with a long phone call and re-create a new password.

Word of warning if you know somebody who uses Bank of America: their customer support has a mechanism to push you a 2nd factor code over SMS and then they actually ask you for the code over the phone. The text message looks 99% identical to the 2nd factor code you get when normally logging in to your bank account.

Support does this to 'verify your identity' and authorize doing arbitrary things like even moving $100,000 out of your bank account.

And no, their security team won't fix this.

Apple needs to help move the needle on 2FA/U2F/webauthn. Unfortunately you can even create an apple Id without a dreaded SMS "authentication".

This may explain why I get called every week from all over Europe by people that think they missed a call from me.

I knew it had to be a scam, but hadn’t put the pieces together.

uh.. No, and NIST has been saying this for about 5 years.

Apple is forcing users who upgrade to Catalina to use 2FA and if you do not have multiple devices this defaults to SMS.

There is no option to turn it off.

Ran Bar-Zik, from Israel, created a technique to hack most voice 2FA by using a weak voicemail password. It was largely used in 2019 to hack Brazilian politicians, including state ministers. The hacked telegram messages were passed to Glenn Greenwald, linked to Assange.

Do you have any sources on that (the specific technique that was used)? Google returned nothing.

AFAIK, they were hacked using plain simple SIM swap/cloning.

https://politica.estadao.com.br/blogs/fausto-macedo/wp-conte...

(Portuguese)

It would be nice if the carriers allowed you to specify you wanted to restrict SIM swapping. When I lost my 3 SIM to get the number transferred to a new one I went to a 3 store with my passport. I'd be fine with that being the only method they'd allow.

I have been saying this for years.

The amount of knowledge one needs to port a phone number is unbelievably little, and peoples very nature to be helpful works against us. Up until maybe just very recently you needed the account number of the phone number and the last four of a social security number... sometimes, just the account number. Also, the last four of one's social security number is perhaps the shittiest way to authenticate _ANYTHING_. For many years, a lot of sites online would show you the last four of an account holder's SSN (and some places still probably do) if you have an email address, correct name, and phone number or physical address.

Getting the account number would likely be even easier thanks to helpful store reps... Just go in and make up an excuse why you need it or forgot it, it's like "social engineering 101" because it seems so benign to most people. You already know the name, address, and phone number-- you just "forgot" your id at home... Or one could just listen to them call each-other write down their info and then call another store.

With those two things in hand, the phone number is pretty much the attacker's, and getting it back would take more than enough time for extensive amounts of damage... ESPECIALLY if that is the only line on the account (or they took all the lines)... I'd guess a bare minimum with near immediate recognition of the real problem (your number heisted) and police involvement, probably a minimum of ~12 hours.

So, if phone numbers are so bad why are they ever used? IMHO, that's because they aren't to provide security, they're to provide easy tracking between your virtual life and your physical one. You're only securing the businesses data pipeline, not your personal data.

If you want 2FA (and everyone should) use Google Authenticator or a Yubikey... or whatever I'm not trying to shill brands just ideas that work.

Unrelated -- I love how the domain name is literally the average Google query for when this becomes breaking news. Clever to make your domain name a literal Google query if you want to spread an idea...

Now I only need to find out on which ones of my 200+ accounts this feature is enabled… Honestly, it would be easier for me if the EU just made it illegal, forcing services to disable it for me.

Why? It's not "secure" but it's more secure than nothing.

The paper mentions some websites that claim to use SMS 2FA, but actually use SMS as a single factor for password resey. While that's really bad I think the solution is to fix those broken implementations not to stop using SMS 2FA everywhere in favor of using nothing.

The paper also said, "websites should eliminate SMS based MFA altogether".

I know a few people who have been hacked with this method via t-mobile in order to control chat rooms on telegram and steal crypto.

According to this paper, t-mobile has the smallest surface area, which is sad.

Why sad? someone has to have the smallest

Would it be less sad if it was Verizon?

To him it's sad because "I know X is vulnerable and X is best" means he's at risk to the same thing as his friend no matter what he does.

Worth having a private number on a low or PAYG plan and use that for your security separate from your main mobile number.

After all, most have a spare phone and great use for those Nokia's.

This is my conclusion too. A payg that you recharge with cash, so it is unliked to your name in the telecom operator databases is the best protection against rogue employees.

What's with all the redacted entries? Without some context, I assume that these are companies that threatened some sort of legal action if their name was published?

Later in the paper they mention that they're temporarily redacted due to responsible disclosure rules.

They say there are 361 sites pulled from TwoFactorAuth.org's list of sites, and they were able to access 145 of them.

In describing the set they initially drew from, it seems like they've described the 17 redacted sites simply by describing their complementary set (the 128 sites that are secure).

http://isThisYourPaperOnSingleServingSites.com/

I wish more websites (and other application protocols) would support client-side certificates in addition to the username and password for authentication.

Where were these five providers based? Was it just in the US? I wonder if the controls are more stringent; my suspicion would be that they are in Europe.

What about google voice? I've noticed a lot of sites block it, but it seems as safe as email for 2fa.

Haven't we known this for quite some time? I'm just amazing many places still use it!

Why don’t they just do two verification charges between .01 and .99 to the card on file.

Could using an im service like Matrix to send the authentication token be more secure?

Does anyone know the reason for all the Redacted entries on the interactive datasets?

So can we finally stop saying it's better to have SMS 2FA then to not have it?!

Short answer: no.

Long answer: nooooooooooo.

Betteridge's law of headlines is an adage that states: "Any headline that ends in a question mark can be answered by the word no".

https://en.m.wikipedia.org/wiki/Betteridge's_law_of_headline...

Not sure why you're getting downvoted, I hadn't heard of this before and found it quite amusing as well as somewhat relevant to the topic, although a blanket statement providing not much value.

My vote would just be not to vote (neutral). There is certainly more (in)appropriate stuff to downvote.

The key part here is to only post this comment under headlines for which the answer in "no".

What I normally do is remember the law, and generally I don’t click through headlines which are questions.

But this one felt more like it would be something a little deeper.

So then I clicked through - and the page fills up with the word “no”.

So I feel pretty duped.

As always, it works (the law, not the SMS 2FA)

I’m surprised I was downvoted too.

Honestly I think the headline is attention grabbing. A much more useful headline would have been “An analysis of the vulnerabilities of 2FA over SMS”.

But the Betteridge headline is in the domain name!

Isn't perfect the enemy of the good, especially in security?

SMS is worse than 1FA.

Would be freaking awesome if Wells Fargo understood this...

People always focus on SIM swaps and signal security, but neither of those apply to Google voice numbers. So in the context of Google voice, is there still any reason to not use SMS 2FA?

Bank of America doesn’t send SMS to google voice phone numbers.

Bank of America won’t send sms to my Canadian carrier either. I have to request a call every time.

What happens if you port to Google voice, can you no longer access your account?

I don't know, all I know is I can't receive BoA 2FA SMS on my Google Voice number. This is what BoA says:

>You are consenting to be contacted at the phone number selected for the purpose of receiving an authorization code. If you selected text message, Wireless and text message fees may apply from your carrier. Supported carriers include: Alltel, AT&T, Cellular One, T-Mobile, Virgin Mobile, U.S Cellular and Verizon Wireless.

Although I just remembered this person on Hacker News replied to me 1+ year ago that their Google Voice number does work with BoA 2FA SMS, so maybe it's just my specific GV phone number?

https://news.ycombinator.com/item?id=18196014

All of my banks and financial services do.

When my gf lived in Malaysia, she added her phone number to FB and forgot about it. Years later, after having moved back to Vietnam, the number was recycled and someone was able to use that number to gain access to her FB account and reset the password.

Getting access back to her account took a bunch of steps, including adding her current number.

The interface for FB really makes it seem like you might lose access to your account if you don't provide them with your number. Even better is that FB exposes a small list of your friends (and the total count) of everyone who has given them their phone number.

tl;dr: Don't add your phone number to FB.

Compared to what?

Better than not having it? Yes.

Better than committing a 4,096Kb PK to memory and confirming all interactions with mental arithmetic? No.

The article says "We found 17 websites on which user accounts can be compromised based on a SIM swap alone", that seems like a pretty clear indication that it can be worse than nothing.

I happen to think the benefits of SMS 2FA, even when working as intended, are negligible. It seems like a bad idea to waste the finite amount of developer good will we have asking services to implement it.

Literally the only attack that SMS 2FA has any impact on is credential stuffing, and even then it's debatable. Credential stuffing is using the credentials stolen from one service to compromise another. If you don't reuse passwords, then you don't need SMS 2FA.

If you do reuse passwords - then it seems impossible you're not also vulnerable to phishing. After all, you're already willing to hand over your credentials to anyone who asks. SMS 2FA is not a solution to phishing, as the tokens themselves can be phished.

If you can compromise the account, based on a SIM swap alone, then that site has 1FA (The phone number).

2FA requires you to have 2 factors at the same time. e.g. When I log onto amazon from a new browser with valid username+password it additionally requires me to confirm via my phone number.

1or1FA (e.g. reset your password via SMS if you forget your password) is just increasing the attack area on 1FA (would be more secure without it).

Problem it's trying to solve, is that it's conventionally unacceptable to lock people out of their accounts.

Let's say that it wasn't you who logged in with a valid username and password, it was an attacker.

Under what circumstances does the phone number prompt prevent the attacker from accessing your account?

Perhaps they used phishing? Then they can just phish the SMS code as well.

Perhaps they're a MITM over an insecure channel? Then they can just wait for you to enter the SMS code.

Perhaps you installed their malware? Then they can just inject some code into the browser.

Compared, presumably, to the other two popular 2FA methods: TOTP and WebAuthn (f/k/a U2F).

From the past few months I'm collecting all resources on the use of SMS as a 2FA: https://github.com/kdeldycke/awesome-iam#sms-based-authentic...

TL;DR: don't.

The TLD is the question, the title is the answer.

No Its not

Hhhhhh yes you can check more details http://www.jobsfinderuae.com/2020/01/accountant-jobs/

Did we ever seriously doubt that? 2FA is just a made-up reason to have your phone number anyway, all the services that require that don't really want anything other than that.

HN seems to be getting a lot of these submissions lately where the question asked in the title is the same as the domain name. Sometimes the content of the page doesn't even answer the question.

Feels like some kind of spammy PageRank manipulation going on. I'm happy to be wrong about this, but I wanted to see if anyone else has noticed. Maybe I'm just smoking crack waffles again.

This is clearly a PR effort associated with the research paper hosted on the site.

It's a single-purpose domain name, so the Name of the domain is the same as the Name of the content on the domain.

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