Stupid but true over 2 years ago some friends and I opened a car chevrolet GM link with the system were the following steps.
1. seek the security module, remove the SIM card.
2. Connect the sim card to the computer, and verify Ki, LAI, SPN, SDN and VAS.
3.With the SIM into the computer, sending commands to open dors, etc, save the commands received.
4. Put simcard back into the security module.
5. Sent from a common cell codes. Result all GM link options.
The Israelis have better security systems and they do send a VPN over the Internet encrypted code.