๐ก The talk is about decoupling the SIM card from the mobile phone or modem to perform various measurements.
๐ Roaming in cellular networks can be complex and interesting due to the differences in configurations, hardware, and software between home and visiting networks.
๐ฐ International travel and testing in different networks can be expensive and tedious.
๐ MobileAtlas decouples SIM cards from modems and enables global connectivity.
โ๏ธ Goals of the project include scalability, automatability, and controlling background noise.
๐ Challenges faced include adapting the SIM interface and protocol for global usage.
๐ง The use of SIM tunneling and Schottky diodes simplifies the negotiation of speeds and voltages between the SIM provider and the modem.
๐ Linux network spaces and binary encoding are used to control background traffic and ensure accurate measurements of data counting.
๐ฒ Bluetooth rSAP protocol allows for the connection and sharing of SIM cards between an Android phone and the system.
๐ SIM tunneling provides an opportunity for carriers to verify services and improve configurations for Voice over LTE roaming.
๐ SIM cards can update or change their unique identifier (IMSI) over the air for roaming purposes.
โ๏ธ USB devices have a practical limit of around 20-30 devices due to hardware and driver limitations.
๐ The system has been deployed to 10 European countries and North America, with some limitations in Canada.
๐ฌ The use of modems instead of software-defined radios is due to regulatory challenges and safety concerns.
๐ก The platform allows for internet-related measurements, including billing and abuse of zero-rating offers.
๐ Different metrics are used for traffic classification, including UDP port, IP address, and deep packet inspection.
๐ The study focused on deep packet inspection and analyzed zero-rating applications like WhatsApp, Snapchat, and Facebook Messenger.
๐งช Experiments were conducted to verify web endpoints' zero-rating, detect IP-based and hostname-based classification methods.
๐ Operators use both IP-based and hostname-based classification for zero-rating traffic.
โ๏ธ Attackers can exploit hostname-based classification by faking host data and spoofing SNI in TLS connections.
๐ Location tracking can be done through ringback tones issued by terminating operators, allowing differentiation between operators.
๐ By analyzing the amplitude and frequency of calls, it is possible to determine the operator and country of the callee.
๐ฑ SIM cards can send covert binary SMS messages without the user's knowledge, containing information about the user equipment.
๐ Roaming is an interesting case where two operators cooperate, and there are ways to exploit it for hiding traffic and locating subscribers.
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