5 ms·

So, the twitter post alludes to SS7, but it is not clear how it is (ab)used to do the Telegram-related exploitation. Presumably, SS7's design flaws are being u

So, the twitter post alludes to SS7, but it is not clear how it is (ab)used to do the Telegram-related exploitation. Presumably, SS7's design flaws are being used intercept Telegram's registration verification messages, placing the resulting Telegram accounts under control of the bad actors while appearing to be real, independent users (and so aiding in establishing their credibility, which leads to other things), but that is a bit... handwave-y.

super256 4y ago
Telegram allows logins per SMS code (they will be rolling out changes in two days). So as long as you knew the number of your victim and have the ability to re-route SMS, you were able to login to other people’s accounts. Of course this can be easily mitigated by setting a “cloud password”, but I guess most people don’t do that.
- rakoo 4y ago
  If this is true, then Signal should be subject to the same weakness no ?
  - input_sh 4y ago
    Nope. First of all, everything's end-to-end encrypted and no chat logs are stored, so even if someone did do that they wouldn't have access to your chat history. Second of all, if someone tries to impersonate you, your contact gets a notification that your encryption keys have changed, ideally making the recepient slightly more vigilant. Finally, Signal has built-in (optional and not on by default) protection for these types of attacks which require a PIN after activating the number on a new device, making SIM swap attacks useless without PIN as the second factor: https://support.signal.org/hc/en-us/articles/360007059792-Signal-PIN#manage_registration_lock https://support.signal.org/hc/en-us/articles/360007059792-Si...
    - rakoo 4y ago
      Indeed, you're right: the worst that can happen is that chat recipients would see a "your security number has changed". But nothing will happen when talking to a whole new person, or when you join a group you've never been in before.
      - tialaramex 4y ago
        But notice that these are all things you could do anyway. Why are we even bothering to impersonate someone else? If local group "Superb Fun for a Superb Owl" is letting in anybody who wants to join, rather than pretending to be party animal Steve, by using SMS interception to impersonate Steve, why wouldn't a cop named Bill just join the group as Bill ? And if they don't want cops, perhaps because they suspect that "Set fire to the mall" will be considered a crime rather than a fun celebration of NFL Glory, they're not going to wave Steve through, they're going to want to check, and they'll discover that's an impersonator not the real Steve.
        rakoo 4y ago
        The impersonator, by definition isn't known. Only the profile being impersonated is. If an activist is part of a private group, and a cop impersonates the activist, they can get all the new messages without raising any doubt. In a lively conversation, the cop can even send messages and expect the activist not to see them. Disappearing messages will help here.
        tialaramex 4y ago
        To make things easier, let's suppose our Activist is named Alice, and our Cop is named Charlie. > The impersonator, by definition isn't known. Only the profile being impersonated is. Charlie isn't able to impersonate Alice's profile because that's encrypted and Charlie doesn't have the key. Charlie can make a fresh profile, but it's not Alice's, although of course Charlie is able to use a stock photo of Alice (if he has one) and name it "Alice". Let's label this Alice2. > If an activist is part of a private group, and a cop impersonates the activist, they can get all the new messages without raising any doubt. Although Alice may be part of a group, Charlie isn't and Alice2 isn't either. Messages sent to Alice (as a group member) are not received by Alice2, who wouldn't be able to decrypt them anyway. Charlie will need to (as Alice2) ask to have Alice2 admitted to the group. Perhaps he can pretend Alice dropped her phone and bought a new one. Depending on what sort of "activist group" this is and the threat level, this may be quite easy or involve an in-person meeting which will be difficult to fake. Of course since apparently you're imagining Alice is actually still around, she presumably tells people Alice2 is an imposter and it's likely this goes very badly for Charlie even if it's not an in-person meeting. > In a lively conversation, the cop can even send messages and expect the activist not to see them. Disappearing messages will help here. If Alice isn't knocked off the network, none of this "impersonation" works. You seem to be imagining Signal is some toy message board system where you can log in as Alice - just need an SMS, but it's nothing like that, that's why subpoenas don't bring anything meaningful back when they ask Signal about phone numbers, Signal doesn't know anything.
  - pretext-1 4y ago
    Yes it is. It’s worse for Telegram though because it gives the attacker access to the chat history too. Telegram does however send a message to all devices when a new device is logging in, so at least you would know. Signal does not do that but your contacts will get a message that your security code changed if they have the option for that enabled, but people generally ignore this message. Both services offer to set an additional pin or password to protect your account.
    - chaosite 4y ago
      > people generally ignore this message. Because it's noisy. You get that message whenever your conversation partner switches phones or re-installs Signal. The reaction on seeing that message is more "enjoy the new phone, what did you get?" than "have you been hacked?"
      - jeroenhd 4y ago
        For most people, sure. If you're conspiring with others to protest against the oppressive Russian government, you may want to pay closer attention, though. You may even want to do physical verification of the keys.
    - ersii 4y ago
      Signal provides a Registration Lock that is available in the settings for preventing this from happening to some degree, it's however opt-in and you need to set and remember a PIN.
      - jhasse 4y ago
        Telegram too.
- shiomiru 4y ago
  > Of course this can be easily mitigated by setting a “cloud password”, but I guess most people don’t do that. I have a faint memory of being forced to set said cloud password, or at least not finding a way to skip the set password screen. So I've always assumed it wasn't entirely uncommon.
baybal2 4y ago
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super256 4y ago

Telegram allows logins per SMS code (they will be rolling out changes in two days). So as long as you knew the number of your victim and have the ability to re-route SMS, you were able to login to other people’s accounts. Of course this can be easily mitigated by setting a “cloud password”, but I guess most people don’t do that.

rakoo 4y ago
If this is true, then Signal should be subject to the same weakness no ?
- input_sh 4y ago
  Nope. First of all, everything's end-to-end encrypted and no chat logs are stored, so even if someone did do that they wouldn't have access to your chat history. Second of all, if someone tries to impersonate you, your contact gets a notification that your encryption keys have changed, ideally making the recepient slightly more vigilant. Finally, Signal has built-in (optional and not on by default) protection for these types of attacks which require a PIN after activating the number on a new device, making SIM swap attacks useless without PIN as the second factor: https://support.signal.org/hc/en-us/articles/360007059792-Signal-PIN#manage_registration_lock https://support.signal.org/hc/en-us/articles/360007059792-Si...
  - rakoo 4y ago
    Indeed, you're right: the worst that can happen is that chat recipients would see a "your security number has changed". But nothing will happen when talking to a whole new person, or when you join a group you've never been in before.
    - tialaramex 4y ago
      But notice that these are all things you could do anyway. Why are we even bothering to impersonate someone else? If local group "Superb Fun for a Superb Owl" is letting in anybody who wants to join, rather than pretending to be party animal Steve, by using SMS interception to impersonate Steve, why wouldn't a cop named Bill just join the group as Bill ? And if they don't want cops, perhaps because they suspect that "Set fire to the mall" will be considered a crime rather than a fun celebration of NFL Glory, they're not going to wave Steve through, they're going to want to check, and they'll discover that's an impersonator not the real Steve.
      - rakoo 4y ago
        The impersonator, by definition isn't known. Only the profile being impersonated is. If an activist is part of a private group, and a cop impersonates the activist, they can get all the new messages without raising any doubt. In a lively conversation, the cop can even send messages and expect the activist not to see them. Disappearing messages will help here.
        tialaramex 4y ago
        To make things easier, let's suppose our Activist is named Alice, and our Cop is named Charlie. > The impersonator, by definition isn't known. Only the profile being impersonated is. Charlie isn't able to impersonate Alice's profile because that's encrypted and Charlie doesn't have the key. Charlie can make a fresh profile, but it's not Alice's, although of course Charlie is able to use a stock photo of Alice (if he has one) and name it "Alice". Let's label this Alice2. > If an activist is part of a private group, and a cop impersonates the activist, they can get all the new messages without raising any doubt. Although Alice may be part of a group, Charlie isn't and Alice2 isn't either. Messages sent to Alice (as a group member) are not received by Alice2, who wouldn't be able to decrypt them anyway. Charlie will need to (as Alice2) ask to have Alice2 admitted to the group. Perhaps he can pretend Alice dropped her phone and bought a new one. Depending on what sort of "activist group" this is and the threat level, this may be quite easy or involve an in-person meeting which will be difficult to fake. Of course since apparently you're imagining Alice is actually still around, she presumably tells people Alice2 is an imposter and it's likely this goes very badly for Charlie even if it's not an in-person meeting. > In a lively conversation, the cop can even send messages and expect the activist not to see them. Disappearing messages will help here. If Alice isn't knocked off the network, none of this "impersonation" works. You seem to be imagining Signal is some toy message board system where you can log in as Alice - just need an SMS, but it's nothing like that, that's why subpoenas don't bring anything meaningful back when they ask Signal about phone numbers, Signal doesn't know anything.
- pretext-1 4y ago
  Yes it is. It’s worse for Telegram though because it gives the attacker access to the chat history too. Telegram does however send a message to all devices when a new device is logging in, so at least you would know. Signal does not do that but your contacts will get a message that your security code changed if they have the option for that enabled, but people generally ignore this message. Both services offer to set an additional pin or password to protect your account.
  - chaosite 4y ago
    > people generally ignore this message. Because it's noisy. You get that message whenever your conversation partner switches phones or re-installs Signal. The reaction on seeing that message is more "enjoy the new phone, what did you get?" than "have you been hacked?"
    - jeroenhd 4y ago
      For most people, sure. If you're conspiring with others to protest against the oppressive Russian government, you may want to pay closer attention, though. You may even want to do physical verification of the keys.
  - ersii 4y ago
    Signal provides a Registration Lock that is available in the settings for preventing this from happening to some degree, it's however opt-in and you need to set and remember a PIN.
    - jhasse 4y ago
      Telegram too.
shiomiru 4y ago
> Of course this can be easily mitigated by setting a “cloud password”, but I guess most people don’t do that. I have a faint memory of being forced to set said cloud password, or at least not finding a way to skip the set password screen. So I've always assumed it wasn't entirely uncommon.

baybal2 4y ago

[dead]