IMSI catchers are hardware components which send out signals to mobile devices, tricking them that the signal is part of the carrier’s network. They then retrieve the IMSI from the phone, as well as the device’s IMEI (International Mobile Equipment Identity) code. With this information, authorities can track real-time movements of the devices they “catch.” They can also force the phone to shut down.
These devices are controversial even when used by law enforcement agencies. London’s police department is known to have purchased them which raised some concerns among privacy advocates. On August 16th, the 6th US Circuit Court of Appeals ruled that warrantless cell phone tracking is legal, citing that there is no expectation of privacy in the data given off by a voluntarily purchased item.
Now, we face the prospect of criminals getting hold of these devices based on a report coming out of Europe. In Czech Republic, the police are aware of an increased use of these IMSI catchers (called Agátas there), but no one has been apprehended while using one. Local police there do have wire(less) tapping technology, but must obtain a warrant to do so. Czech authorities are not sounding an alarm on this issue, pointing out that there are possible legitimate uses for the technology in the commercial space, such as security firms or certain types of businesses. They concede though, that the technology would be useful to criminals looking to use such gathered information for purposes of extortion.
sources: Slate, Radio Prague