After ADS-B launch, security concerns raised

 - September 14, 2006, 6:00 AM

In one of the FAA’s more unusual program launches, agency Administrator Marion Blakey publicly announced last month the formal launch of the nationwide ADS-B project, a month before her senior bureaucrats were due to decide whether to adopt the system, and six weeks after other top-ranking officials had decreed the removal of ADS-B aircraft targets from controllers’ radar scopes at Anchorage Center.

As if the program launch did not have enough obstacles, last month the former chief of the Australian air safety authority issued a statement saying that he had learned from the FAA that ADS-B was vulnerable to mischievous interference.  In fact,  he suggested that hackers could introduce as many as 50 false targets onto controllers’ radar screens.

It is unclear why Blakey decided to go public before the Joint Resources Council (JRC) gave its approval to proceed. One Washington source stated that in her ongoing battle with the controllers’ union, which by then had reached Congress, she needed to demonstrate to the legislators that she had a firm vision of the FAA’s future direction and a commitment to pursuing it, two qualities many of her predecessors lacked.

Another source suggested that while the JRC approval was a foregone conclusion, Blakey had become concerned that its formal follow-on process could be labored, and that a public program launch was required.

The disruption the formal process could yield was meanwhile being illustrated in Alaska. On March 24, after investigating a report that there had been, in the FAA’s words, a “mis-application” of separation procedures between radar and ADS-B targets at the Anchorage ARTCC, Washington officials ordered the ADS-B returns to be removed from controllers’ displays. It turned out that while one center procedure covered separation standards between two non-ADS-B radar targets and another specified separations between two ADS-B aircraft, there never had, since Capstone’s commencement in 2000, been standards for separating non-ADS-B and ADS-B traffic.

The FAA maintains that safety was never compromised. Nevertheless, instead of issuing an immediate, albeit temporary, instruction to impose non-radar “procedural” separations in such situations, the agency removed ADS-B targets from the center’s radar scopes.

By late May, with ADS-B aircraft still invisible to controllers, a frustrated Alaska Aviation Coordination Council announced it would hold a June 2 press briefing to outline its safety concerns. FAA officials hastily informed the council that ADS-B would promptly reappear at the ARTCC, and issued their own announcement on June 2, stating that procedural separations would henceforth be used.

However, Washington announced that it would take two weeks for the ADS-B targets to return to the controllers’ radar, and  that an operational validation of this “mixed environment,” ostensibly to ensure safety, would begin on July 15.

FAA officials did, however, have other things on their minds during that period. While completing program justifications for their briefing to the JRC on June 7– where Blakey’s announcement was endorsed, as expected–disturbing reports from Australia about ADS-B’s vulnerability to computer hackers became public.

Dick Smith, who has served as chairman of Australia’s Civil Aviation Administration and chaired its Civil Aviation Safety Authority, raised the issue in an open letter to Australia’s Minister of Transport on June 6, one day before the JRC’s meeting. Smith wrote that FAA officials had become aware that with the use of a general aviation transponder, a laptop computer and a $5 antenna, a talented hacker “can create 10, 20 or even 50 false aircraft on an air traffic controller’s screen.”

The FAA was reported as saying that the agency’s Washington office had not provided such information.

Smith further stated that the FAA was “very concerned” about this threat, and was looking at signal encryption or the use of multiple ground stations to separate moving aircraft from fixed “spoofers.” But such steps, noted Smith, would increase the cost of ADS-B by “many multiples.” Industry sources confirmed to AIN that various forms of interference were possible, and that wide area multilateration– where aircraft transponder returns are triangulated to determine their position– rather than additional ADS-B ground stations, could be a less expensive way
to differentiate between moving and fixed targets, and that computer processing could quickly remove the latter from controllers’ screens, or prevent them from appearing. The FAA told AIN that bidders for the ADS-B ground station contract would be required to cover such aspects in their technical proposals.

Earlier, Smith had expressed his concern about the security aspects of real-time tracking of ADS-B-equipped aircraft using commercially available transponder monitors (AIN, May, page 48). While these systems do not radiate spoofing signals, Smith warned that besides exposuring private and commercial aircraft to real-time positioning and monitoring, these devices allow adversaries to track military flights and criminal elements to monitor the movements of law-enforcement aircraft.