Plane & Pilot
Tuesday, May 7, 2013

No Ghosts In The Air…No Privacy, Either!

The Great ADS-B Scare of 2012

ADS-B does raise privacy issues. The Planefinder website collects worldwide data from enthusiasts with ADS-B receivers and displays aircraft positions in real time.
It sounded impressive, and the general press picked up on it—not helped by an FAA response that described ADS-B security issues as too sensitive for public discussion. But, after talking to experts in a position to know how the system really works, I can tell you that any attempt to inject "ghost" aircraft into the U.S. air traffic control system will be a lot more difficult than what was described at Black Hat.

Why? Because you have to consider the air traffic control system as a whole, not just a single aircraft or ground station. The airline pilot in that scenario is flying on an IFR flight plan in controlled airspace. He's being monitored by an air traffic controller. In most U.S. airspace, he'll be seen on primary or secondary surveillance radar—and as we reported back in 2010 (and confirmed for this story by an FAA spokesperson), those radars aren't going away—all primary surveillance radars and half of today's secondary surveillance radars are being retained (some of which are paid for by the U.S. Air Force and the U.S. Department of Homeland Security). The presumed horde of ghost airplanes appear only on ADS-B, not on radar. ATC immediately knows they're bogus (this happens automatically, in a fraction of a second) and doesn't issue instructions to the pilot to deviate around them.

What if it happens in non-radar airspace? At all but the lowest altitudes, airplanes are covered by more than one ADS-B ground station. If only one station receives the signal, it's bogus. Depending on the particular kind of data link used, even a single station may be able to determine whether the ghost is real, based on signal timing. Finally, ATC computers will be looking to determine whether targets are moving appropriately. Does this mean the system is completely secure? Certainly not—but it's a lot more difficult to hack than what was alleged at Black Hat!

In fact, ADS-B makes it safer and more secure to fly—because for the first time, it provides a completely redundant backup to the existing radar-based infrastructure. Today, radar outages can and do lead to long delays and, if unmonitored, can create safety issues. And while it's rare, radar is vulnerable to jamming and spoofing. With ADS-B and radar complementing each other, the system as a whole becomes safer and more secure.
ADS-B won't make U.S. airspace less secure—far from it. It will enchance the safety and security of all operators.
That said, there's one element in the "Ghost Is In The Air (Traffic)" presentation that's quite legitimate. It involves privacy rather than security.


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