A team of suspected crooks who used an “IMSI catcher” to suck up the telephone data of Ile-de-France residents has just been arrested by the judicial police. Denis Jacopini, computer forensic expert who heads the company Lenetexpert, specializing in cybersecurity, explains how this device works and what it is used for.
What is an IMSI Catcher?
DENIS JACOPINI It is a portable relay antenna that picks up communications. And spy specialists can use it in a slightly roundabout way. This device intercepts information that comes and goes on phones. He is also capable of retransmitting others or of transforming them. This is why it can be used to create fake messages, fake SMS or fake conversations. It can be a bank order for a payment. There are also those who validate the receipt of a package.
How does this machine work?
It does not have a range of more than a hundred meters. It’s to hit a specific target. You can drive through a city hanging up all the phones. The devices we all have in our pockets are looking for the strongest signal to connect to a repeater. I see a difficulty. The machine sends messages to all people around this point. But when the vehicle is rolling, people who are still within range are going to get duplicate or triple messages and I find that quite disorganized.
What parade can we implement to protect ourselves from this system?
It is a manual and voluntary action and the telephone today is not at all protected against it. It is necessary to have an application available on Android which has in memory all the relays installed on the territory. It compares the antenna the phone is connected to against its database. If the program discovers a relay which is not listed, it gives the alert.