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On the topic of phreaking, does anyone know if modern condo entryphone systems are vulnerable? The fact that pressing a button on my phone unlocks the front do

On the topic of phreaking, does anyone know if modern condo entryphone systems are vulnerable? The fact that pressing a button on my phone unlocks the front door to the building makes me wonder how it could possibly not be vulnerable to having the right pitches played, but I would hope that the dangers of in-band signalling have been widely understood for long enough that systems would be protected...

mulmen 9y ago
I would be shocked if there are not vulnerabilities in the form of default codes and factory resets. As far as phreaking there's probably something to it. The fact that my building's call box picks up when I dial the front door number seems like a bad sign. The building next to mine has what appears to be an Android tablet as the keypad, I can only imagine the vulnerabilities there.
kkielhofner 9y ago
I assume this is one of those systems where a potential entrant types a code, and the systems calls a pre-provided number for the occupant of the unit who provided the code to the entrant? The common denominator on the PSTN is listening for inband DTMF within a G.711 "encoded" stream. The "security" in this system is the condo entry phone device dialing out to the PSTN (via some mechanism) to the destination number, which is routed via SS7 to the proper owner. This security mechanism is somewhat similar to those used by two-factor systems that send SMS via SS7 to destination numbers. It's not without fault, there have been many demonstrated attacks against the SS7 network.
- cperciva 9y ago
  Sorry, I should have specified more. This is a "potential entrant selects the person they're trying to visit; system phones the pre-programmed number for that occupant; occupant talks to the visitor and presses a button to let them in". In my building, I have to press 6 to make the door unlock. Could a vistor play a very loud "touchtone phone 6" into the microphone and make the system think that the occupant pressed that number?
  - mulmen 9y ago
    That would require the audio signal to be a single channel right? That or the residents phone would have to be very loud. I'm not sure but I think phones operate on a dual channel (tx/rx) setup which is what allows all participants to talk simultaneously.
    - cperciva 9y ago
      I was thinking echoing. I don't know how loud a button tone needs to be for the entryphone system to accept it as an instruction to unlock the door.
- mulmen 9y ago
  To be clear, it uses a similar mechanism to 2FA messages to place the call but there is only one authentication factor in this case. My question is what kind of trouble can I cause by calling the inbound number from my call box? It picks up so presumably it is listening to something. Also, how is the physical security of these devices? Are they managed from the keypad or is the control inside the building in a secure area? How does the FD get in?
lathiat 9y ago
I realise the thread is phone phreaking related and that was kind of the point of your post; but in the spirit of the talk below to think more outside the box... There's a pretty good chance in many cases you can just open the external box with some easy to get (and relatively standard) key. And hit a button. Related: https://twitter.com/MalwareTechBlog/status/903823478167527424 https://twitter.com/MalwareTechBlog/status/90382347816752742... This is a good related talk - goes outside the box on all the ways you can often get into commercial buildings without picking (or even in many cases, interacting with) the lock "The Search for the Perfect Door" by Deviant Ollam https://www.youtube.com/watch?v=4YYvBLAF4T8 https://www.youtube.com/watch?v=4YYvBLAF4T8 Also good: https://www.youtube.com/watch?v=a9b9IYqsb_U https://www.youtube.com/watch?v=a9b9IYqsb_U [Howard Payne & Deviant Ollam - This Key is Your Key, This Key is My Key] https://www.youtube.com/watch?v=oHf1vD5_b5I https://www.youtube.com/watch?v=oHf1vD5_b5I [DEF CON 22 - Deviant Ollam & Howard Payne - Elevator Hacking - From the Pit to the Penthouse]

mulmen 9y ago

I would be shocked if there are not vulnerabilities in the form of default codes and factory resets. As far as phreaking there's probably something to it. The fact that my building's call box picks up when I dial the front door number seems like a bad sign. The building next to mine has what appears to be an Android tablet as the keypad, I can only imagine the vulnerabilities there.

kkielhofner 9y ago

I assume this is one of those systems where a potential entrant types a code, and the systems calls a pre-provided number for the occupant of the unit who provided the code to the entrant? The common denominator on the PSTN is listening for inband DTMF within a G.711 "encoded" stream. The "security" in this system is the condo entry phone device dialing out to the PSTN (via some mechanism) to the destination number, which is routed via SS7 to the proper owner. This security mechanism is somewhat similar to those used by two-factor systems that send SMS via SS7 to destination numbers. It's not without fault, there have been many demonstrated attacks against the SS7 network.

cperciva 9y ago
Sorry, I should have specified more. This is a "potential entrant selects the person they're trying to visit; system phones the pre-programmed number for that occupant; occupant talks to the visitor and presses a button to let them in". In my building, I have to press 6 to make the door unlock. Could a vistor play a very loud "touchtone phone 6" into the microphone and make the system think that the occupant pressed that number?
- mulmen 9y ago
  That would require the audio signal to be a single channel right? That or the residents phone would have to be very loud. I'm not sure but I think phones operate on a dual channel (tx/rx) setup which is what allows all participants to talk simultaneously.
  - cperciva 9y ago
    I was thinking echoing. I don't know how loud a button tone needs to be for the entryphone system to accept it as an instruction to unlock the door.
mulmen 9y ago
To be clear, it uses a similar mechanism to 2FA messages to place the call but there is only one authentication factor in this case. My question is what kind of trouble can I cause by calling the inbound number from my call box? It picks up so presumably it is listening to something. Also, how is the physical security of these devices? Are they managed from the keypad or is the control inside the building in a secure area? How does the FD get in?

lathiat 9y ago

I realise the thread is phone phreaking related and that was kind of the point of your post; but in the spirit of the talk below to think more outside the box... There's a pretty good chance in many cases you can just open the external box with some easy to get (and relatively standard) key. And hit a button. Related: https://twitter.com/MalwareTechBlog/status/903823478167527424 https://twitter.com/MalwareTechBlog/status/90382347816752742... This is a good related talk - goes outside the box on all the ways you can often get into commercial buildings without picking (or even in many cases, interacting with) the lock "The Search for the Perfect Door" by Deviant Ollam https://www.youtube.com/watch?v=4YYvBLAF4T8 https://www.youtube.com/watch?v=4YYvBLAF4T8 Also good: https://www.youtube.com/watch?v=a9b9IYqsb_U https://www.youtube.com/watch?v=a9b9IYqsb_U [Howard Payne & Deviant Ollam - This Key is Your Key, This Key is My Key] https://www.youtube.com/watch?v=oHf1vD5_b5I https://www.youtube.com/watch?v=oHf1vD5_b5I [DEF CON 22 - Deviant Ollam & Howard Payne - Elevator Hacking - From the Pit to the Penthouse]