A simple trick could disable a city’s 4G phone network

High-speed wireless data networks are vulnerable to a simple scrambling technique that could block service in much of the city, according to the results of research provided to a federal agency last week.

LTE broadband mobile network technology (long-term evolution) is spreading rapidly around the world. But researchers have shown that a single, low-cost, battery-powered transmitter targeting very small portions of the LTE signal could knock out a large LTE base station serving thousands of people. “Imagine a scrambler who fits in a small briefcase and removes miles of LTE cell phone jammer, whether it’s commercial or public safety,” said Jeff Reed, director of the Virginia Wireless Technology Research Group. Tech.

“It can be relatively easy to do,” says Reed, and it would not be easy to defend oneself. If a hacker added an inexpensive power amplifier to his malicious platform, he could destroy an LTE network in an even larger region.

If LTE networks were to be compromised, existing 3G and 2G networks would continue to operate, but these older networks are being phased out.

Reed and a research assistant, Marc Lichtman, described the vulnerabilities in a case filed last Thursday with the National Telecommunications and Information Administration, which advises the White House on telecommunications and information policy. NTIA did not respond immediately as it solicited expert input on the possibility of using LTE for communications with emergency responders.

Any radio frequency can be blocked or “blocked” if a transmitter sends a signal at the same frequency, with enough power. But LTE is particularly vulnerable, according to Reed’s group. Indeed, the entire LTE signal depends on control instructions representing less than 1% of the overall signal.

Some of these instructions govern the critical timing and frequency that underlie LTE transmissions. “Your phone constantly syncs with the base station” to effectively transport and assemble pieces of information that make up, for example, a photo or video, says Lichtman, a graduate research assistant who co-authored ‘study. “If you can interrupt this synchronization, you will not be able to send or receive data.”

The researchers explain that there are seven other weak points of this type, one of which could be used to scramble an LTE signal with a low power transmitter. “There are several weak points: about eight different attacks are possible. The LTE signal is very complex and consists of many subsystems. In each case, if you delete a subsystem, you delete the entire base station. ”

All that would be needed would be a laptop and a low-cost software-defined radio unit (which can cost as little as $ 650). The power of the battery, including that of the car, would then be sufficient to block an LTE base station. This would require technical knowledge of the complexity of the LTE standard, but these standards, unlike military standards, are openly published. “Any communications engineer would be able to solve this problem,” says Lichtman.

Lichtman proposed the analogy of preventing all cars, taxis and trucks from circulating in Manhattan by silencing the signaling system. “Imagine blocking all traffic lights so that no one can see if they are red or green and what happens to the traffic. The cars collide and nobody gets through, “he says.

All the latest smartphones and key operators strongly favor the transition to LTE networks. Nearly 500 million people worldwide have access to the signals of more than 100 LTE operators in 94 countries. Technology can be 10 times faster to transmit data, such as video, than 3G networks. Reed’s group did not determine if anything could be done to resolve the newly identified problem. “You must first put the issues on the agenda. Although we have identified the problem, we do not necessarily have solutions, “he says. “It is practically impossible to put in place mitigation strategies that are compatible with previous versions and covering all that.”

But LTE is also proposed as the basis for next-generation communication systems for emergency response – a proposal called FirstNet, designed after communication problems