Stray Signals

The radio navigation planes use to land safely is insecure and can be hacked – Ars Technica

A plane in the researchers' demonstration attack as spoofed ILS signals induce a pilot to land to the right of the runway.

Just about every aircraft that has flown over the past 50 years—whether a single-engine Cessna or a 600-seat jumbo jet—is aided by radios to safely land at airports. These instrument landing systems (ILS) are considered precision approach systems, because unlike GPS and other navigation systems, they provide crucial real-time guidance about both the plane’s horizontal alignment with a runway and its vertical angle of descent. In many settings—particularly during foggy or rainy night-time landings—this radio-based navigation is the primary means for ensuring planes touch down at the start of a runway and on its centerline.

Like many technologies built in earlier decades, the ILS was never designed to be secure from hacking. Radio signals, for instance, aren’t encrypted or authenticated. Instead, pilots simply assume that the tones their radio-based navigation systems receive on a runway’s publicly assigned frequency are legitimate signals broadcast by the airport operator. This lack of security hasn’t been much of a concern over the years, largely because the cost and difficulty of spoofing malicious radio signals made attacks infeasible.

Now, researchers have devised a low-cost hack that raises questions about the security of ILS, which is used at virtually every civilian airport throughout the industrialized world. Using a $600 software defined radio, the researchers can spoof airport signals in a way that causes a pilot’s navigation instruments to falsely indicate a plane is off course. Normal training will call for the pilot to adjust the plane’s descent rate or alignment accordingly and create a potential accident as a result.

One attack technique is for spoofed signals to indicate that a plane’s angle of descent is more gradual than it actually is. The spoofed message would generate what is sometimes called a “fly down” signal that instructs the pilot to steepen the angle of descent, possibly causing the aircraft to touch the ground before reaching the start of the runway.

The video below shows a different way spoofed signals can pose a threat to a plane that is in its final approach. Attackers can send a signal that causes a pilot’s course deviation indicator to show that a plane is slightly too far to the left of the runway, even when the plane is perfectly aligned. The pilot will react by guiding the plane to the right and inadvertently steer over the centerline.

The researchers, from Northeastern University in Boston, consulted a pilot and security expert during their work, and all are careful to note that this kind of spoofing isn’t likely to cause a plane to crash in most cases. ILS malfunctions are a known threat to aviation safety, and experienced pilots receive extensive training in how to react to them. A plane that’s misaligned with a runway will be easy for a pilot to visually notice in clear conditions, and the pilot will be able to initiate a missed approach fly-around.

Another reason for measured skepticism is the difficulty of carrying out an attack. In addition to the SDR, the equipment needed would likely require directional antennas and an amplifier to boost the signal. It would be hard to sneak all that gear onto a plane in the event the hacker chose an onboard attack. If the hacker chose to mount the attack from

Read the full article at https://arstechnica.com/information-technology/2019/05/the-radio-navigation-planes-use-to-land-safely-is-insecure-and-can-be-hacked/. STRAY SIGNALS does not claim ownership of the article. The original author is responsible for the content of this post

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