Air traffic system vulnerable to cyber attack

Next-generation global air traffic control system is vulnerable to malicious hacks that could cause catastrophe

An alarm blares in the cockpit mid flight, warning the pilot of an imminent collision. The pilot checks his tracking display, sees an incoming aircraft and sends the plane into a dive. That only takes it into another crowded air lane, however, where it collides with a different plane. Investigators later discover that the pilot was running from a "ghost" - a phantom aircraft created by a hacker intent on wreaking havoc in the skies.

It's a fictional scenario, but US air force analysts warn that it could be played out if hackers exploit security holes in an increasingly common air traffic control technology.

At issue is a technology called Automatic Dependent Surveillance - Broadcast (ADS-B), which the International Civil Aviation Organisation certified for use in 2002. Gradually being deployed worldwide, ADS-B improves upon the radar-based systems that air traffic controllers and pilots rely on to find out the location and velocity of aircraft in their vicinity.

Conventional ground-based radar systems are expensive to run, become less accurate at determining position the further away a plane is, and are slow to calculate an aircraft's speed. Perhaps worst of all, their limited range means they cannot track planes over the ocean.

So instead of bouncing radar signals off aircraft, ADS-B uses GPS signals to continuously broadcast a plane's identity, ground position, altitude and velocity to networks of ground stations and other nearby aircraft. This way, everyone knows where everyone else is.

ADS-B transmits information in unencrypted 112-bit bursts - a measure intended to make the system simple and cheap to implement. It's this that researchers from the US air force's Institute of Technology at Wright-Patterson Air Force Base in Ohio are unhappy with. Donald McCallie, Jonathan Butts and Robert Mills warn that the unencrypted signals could be intercepted and spoofed by hackers, or simply jammed.

The team says the vulnerabilities it has identified "could have disastrous consequences including confusion, aircraft groundings, even plane crashes if exploited by adversaries" (International Journal of Critical Infrastructure Protection, DOI: 10.1016/j.ijcip.2011.06.001).