Let me share what I know about this security system and how easy it is to hack it.
As stated previously here, cars like the innova, swift etc which have the immobilizer system, work on the basis of a transponder which is installed in the key and the sensor for the same which is located near the ignition keyhole. Its not easy to duplicate this transponder as it requires specialized and expensive tools and more importantly physical access to the key. Which is easier said than done.
So the thieves have figured out that the key is matched to the ecu and a simple way to get around the whole thing is to get an ECU and a matched key, gain access to the engine bay and then replace said ECU with the matched one and simply drive off.
But in the case of more expensive cars like BMW, Mercedes and Audi there are two very hi tech forms of theft which is used.
1. The first method involves taking advantage of a flaw in the keyless start feature which is present in these vehicles, There are a lot of articles online (just search for "Hi tech car theft") which go into very minute detail, but ill keep it simple for easy understanding. Basically, the keyless start system also comes with a keyless unlock which requires you to simply touch a button on the door handle or on the sensor behind the handle. So in order for this system to work seamlessly, an encrypted signal is sent in frequent intervals which when detected by the key is responded to with a verification code which in turn unlocks the vehicle. The signal sent by the car covers a maximum radius of around 1.5 meters around the car, but the signal sent by the key can cover nearly 300 meters. So what these people do is use a simple device that amplifies the signal sent by the car to nearly a kilometer in radius so that the remote may send back the verification code and the car would think that the key is in the vicinity, once this is done, the doors can be unlocked and the same process is repeated inside the car to make the car think that the key is present inside the vehicle. This flaw was detected as early as two years back when several surveilence videos emerged of thieves simply walking by a car and unlocking it just by touching the handle or even by simply standing there. There were several cases of such people simply driving off with vehicles but none, if not a very few of them involved newer german luxury cars. Here is where the second technique comes into play.
Heres a video of this particular method which appeared on an American news channel.
New High tech car theft device showing up in the US
2. This process is used almost exclusively with BMW's and that too newer ones, there are videos of the 1M being stolen, a 530D being stolen all on youtube, in fact in an interview with the owner of the 5 series on a news channel, he said that the insurance company refused to believe that such a high tech car could be stolen at all in this day and age. But it was the surveillance camera footage that saved him. Back to the topic, this process involves three steps,
a. gaining access to the interior of the car without setting off the shock sensor and the interior movement sensor.
b. Plugging in a specialized handheld tool into the OBD port of the vehicle and programming a blank key to match the vehicle.
c. Dropping the car into neutral after turning it into acc mode to roll the vehicle from garage/parking lot to a safer spot and then simply driving it off.
Heres the picture of the said device.
Video of a brand new BMW 1M being stolen in the UK.
Here are some links which give further info on the same.
BMW's can be stolen in 3 minutes or less Keyless BMW's prove to be very easy to steal