The lack of security in communication technologies used in the aviation industry makes it possible to remotely exploit vulnerabilities in critical on-board systems and attack aircraft in flight, according to research presented Wednesday at the Hack in the Box security conference in Amsterdam.

The presentation, by Hugo Teso, a security consultant at consultancy firm N.runs in Germany, who has also had a commercial pilot license for the past 12 years, was the result of the researcher’s three-yearlong research into the security of avionics.

Teso showed how the absence of security features in ADS-B (automatic dependent surveillance-broadcast), a technology used for aircraft tracking, and ACARS (Aircraft Communications Addressing and Reporting System), a datalink system used to transmit messages between aircraft and ground stations via radio or satellite, can be abused to exploit vulnerabilities in flight management systems.

He did not experiment on real airplanes, which would be both dangerous and illegal, according to his own account. Instead Teso acquired aircraft hardware and software from different places, including from vendors offering simulation tools that use actual aircraft code and from eBay, where he found a flight management system (FMS) manufactured by Honeywell and a Teledyne ACARS aircraft management unit.

Using these tools, he set up a lab where he simulated virtual airplanes and a station for sending specifically crafted ACARS messages to them in order to exploit vulnerabilities identified in their flight management systems—specialized computers that automate in-flight tasks related to navigation, flight planning, trajectory prediction, guidance and more.

The FMS is directly connected to other critical systems like navigation receivers, flight controls, engine and fuel systems, aircraft displays, surveillance systems and others, so by compromising it, an attacker could theoretically start attacking additional systems. However, this aspect was beyond the scope of this particular research, Teso said.

Identifying potential targets and gathering basic information about them via ADS-B is fairly easy because there are many places online that collect and share ADS-B data, such as flightradar24.com, which also has mobile apps for flight tracking, Teso said.

ACARS can be used to gather even more information about each potential target, and by combining this information with other open-source data, it is possible to determine with a fairly high degree of certainty what model of FMS a specific aircraft is using, Teso said.

After this is done, an attacker could send specifically crafted ACARS messages to the targeted aircraft to exploit vulnerabilities identified in the code of its FMS. In order to do this, the attacker could build his own software-defined radio system, which would have a range limit depending on the antenna being used, or he could hack into the systems of one of the two main ground service providers and use them to send ACARS messages, a task that would probably be more difficult, Teso said.

Either way, sending rogue ACARS messages to real aircraft would most likely lead to the authorities searching and eventually locating you, the researcher said.

Teso created a post-exploitation agent dubbed SIMON that can run on a compromised FMS and can be used to make flight plan changes or execute various commands remotely. SIMON was specifically designed for the x86 architecture so that it can only be used in the test lab against virtual airplanes and not against flight management systems on real aircraft that use different architectures.

The researcher also created an Android app called PlaneSploit that can automate an entire attack, from discovering targets using Flightradar24 to exploiting vulnerabilities in their FMS, installing SIMON and then performing various actions, like modifying the flight plan.

As previously mentioned, the research and demonstrations were performed against virtual planes in a lab setup. However, the FMS vulnerabilities identified and the lack of security in communication technologies like ADS-B and ACARS are real, Teso said

In a real-world attack scenario, the pilot could realize that something is wrong, disengage the auto-pilot and fly the plane like in the old days using analog systems, Teso said. However, flying without auto-pilot is becoming increasingly difficult on modern aircraft, he said.

Teso did not reveal any specifics about the vulnerabilities he identified in flight management systems because they haven’t been fixed yet. The lack of security features like authentication in ADS-B and ACARS is also something that will probably take a lot of time to address, but the researcher hopes that it will be done while these technologies are still being deployed. In the U.S., the majority of aircraft are expected to use ADS-B by 2020.

N.runs has been in contact with the European Aviation Safety Agency (EASA) for the past few weeks about the issues identified during this research, Teso said, adding that he has been pleasantly surprised by their response so far. “They haven’t denied the issues, they listened to us and they offered resources,” he said. “They’re trying to help us to take this research on a real plane.”