I'm Aaron Grelias. I'm a security researcher with Grimm. I'm on the cyber physical systems team.
We work on improving the security of embedded devices everywhere. I've also got a background,
a long background in embedded software development on critical systems,
the telecom, aerospace, medical, and a bunch of different fields.
My name is Tim Brown. I run the cyber physical systems team here at Grimm. I've been at Grimm
for about five years now, hacking all sorts of different types of embedded systems from
aerospace to automotive, heavy trucking, medical.
And we're here today to talk about some of where cybersecurity meets aviation regulations.
I'm going to start by talking about the current status of cybersecurity regulation.
And more how software development happens in aerospace.
The current process that we have descends from the, historically, how airlines have
approached the topic of safety. Airlines have approached the topic of safety,
usually, historically, from a purely mechanical standpoint. This part will last for about this
long in airplanes. It has to be replaced every so often. There's maintenance procedures and
airworthiness directives that talk about how often these parts need to be replaced based on
how long it takes them to fail. There's things that they test, like anywhere you have stresses
on a metal joint, you'll have testing done, both visual inspection and other types of testing,
depending on circumstances, to see if it's starting to fail, if it's starting to get
cracks forming in those areas. But it's really designed around this concept that
once you make a part, it behaves in some sort of defined way that doesn't change. Once you design
it, do all your fairly rigorous testing that they do in the airline, the aerospace industry,
and install it, it will change in ways that are defined, essentially, by the physics of the
situation. Stresses on metal, opening and closings of latches, and stuff like that,
that have a defined physical characteristic. And you can define maintenance procedures that will
detect all of these potential issues on the airplane. Maintenance procedures are defined
to replace things that need to be replaced periodically. These maintenance procedures
you can follow in the commercial aerospace world will be followed. They rely on that happening,
that does happen. And they do it in places like this. They have drawers that have
labeled places for every bit, every socket, every tool. It's access controlled. So you know that
when you do your maintenance procedure, there's a procedure for using this size socket to remove
these bolts and you put it back when you're done. So you don't wind up leaving a socket in an
airplane. They have these fairly strictly defined procedures that you follow in order to make sure
that all these maintenance is done correctly and done completely. So that's the kind of history
of where we came from. As far as the current regulations that drive the software development
process for modern aviation software, that's regulated at least in this country and many
other ones by something called DO-178C. We're not going to go into this too deeply, but
knowing how things work right now and how levels of safety are defined will help us think about
cybersecurity and how to go forward with that. This is developed by RTCA. It stands for Radio
Technical Commissions for Aeronautics, which I never actually knew until I looked that up.
It's not super important. It's just an organization that develops a bunch of aviation standards.
And again, these are adopted by FAA in the United States, Transport Canada, and European Aviation
Safety Agency, EASA. So what is DO-178C? I like to summarize it this way. You basically tell
the FAA... well, a DER is the designated representative that stands in for the FAA.
Tell them how you plan on designing, creating, and testing your software. And then you go and
follow your plan and do those things. And then you have to prove that you followed your plan.
That's it in a nutshell. Now there's a lot more paperwork involved. There's a lot of checklists
you do have to go through and make sure that your plan actually does identify all the areas of
concern that DO-178C points out. And if the DER thinks that anything is lacking in your plan,
they will tell you and help you make sure that it gets revised appropriately.
That's the way things go forward right now. And as you can see, it's kind of a very
waterfall-y based model where you do all your design up front, you create a design,
you create a spec, the actual product that implements the design, then you do testing on it
in order to make sure that the product design actually meets the requirements that
the product was supposed to fulfill. That is a good point. The way this does work in practice,
it is extremely waterfall. There have been attempts to try and figure out how to fit
Agile methods into this, but it is very much plan, do, prove. Just pretty much in those steps.
And this again comes from that historical background of making mostly mechanical
components where that is how you design them. You don't do iterative development on,
you know, a weight usually. I mean, if there's issues, you'll go back and fix them of course,
but like you don't really do, you know, there is no fail fast on making a lot of these
mechanical components. So it's trying to shoehorn software development
into how they make mechanical components for these aircraft.
And as anybody who's been in software development for a while knows that
waterfall has been around for a long time. The DO-178C categorizes different levels of software
according to the potential consequences of a failure of that software.
So levels A through E, and basically A means that something catastrophic would happen
if it fails. Level E means that nothing is going to happen safety wise, you know,
maybe the passengers can't watch movies, right? That would be a level E software.
The level A is also the highest cost. This is probably unsurprising.
The last numbers I can find show that it's estimated to be about $100 per line of code
for level A software. They're not all software on an airplane is level A. It's usually just as
small percentage as possible because of the cost. But Boeing 787, for example,
is estimated to have between 6 and 7 million lines of code. So even if it's a small percentage,
just the level of certification alone of the software drives a great deal of cost.
Basically, these go from different levels. So level A, catastrophic software, usually
software that is level A rated will have autonomous control, which means that there's
no way to intervene if something fails, hence why it's so expensive and so time consuming to develop.
Then they go on both. Level B would be something where something hazardous could happen,
but also level B will typically allow for pilot intervention. So it might be something that
significantly increases the workload or the challenge of flying the aircraft,
but it would be something that can be addressed by the pilot training.
Level A and B is usually loss of life. A level A failure was likely to lead to loss of life.
Level B failure is not likely to lead to loss of life or severe injury.
Injury sustained in a level B failure should be minimal.
And then it goes on down from there. C and D are major minor impacts to the flight of the aircraft.
Also, so entertainment systems are going to be level E, means that there's
lower, less regulations and less checklists, essentially. As you go down in level,
you have to do less to prove in that proof step.
In DO-178C, code is expensive. So stuff, especially if it's a level B or level A,
very unlikely to have unused code in it or unnecessary code in it, like a shell onto a
system. DO-178A, you're not allowed to have dead code in your design on the system.
Because it's so expensive to develop the code, there's usually a minimal amount of code
on these systems. There is extensive testing done for the higher certification levels.
There's at least a significant quantity of testing done. Pilot training on how to use the software
is... the systems are designed for redundancy and safety. So if you do have a failure,
there should be a redundant system to back up that failure. Unless you have a 737 MAX,
we won't talk about that right now. Very limited interfaces on these flight-critical systems.
They use interfaces like RN429. RN429 is a UART-style bus. You're limited to sending
32 bits of data at a time. There's not really room for buffer overflow here. You don't really
have longer messages on top of RN429. These interfaces are very strictly defined and fairly
provide very limited functionality beyond just sending the necessary critical data
back and forth on the bus. There's a great deal of emphasis on determinism and reliability.
So there's some bad things related to the current way software is defined and designed
in aerospace. This is kind of... so as I said, you know, as we said, both Tim and I have worked
in aerospace kind of on the development side of things and also on the cybersecurity testing side
of things. The things that... I found many things frustrating when I was doing on the development
side of things. This is kind of the... a piece of that list right here. Data validation is guarding
against accidental data modification. The design of how software is made to be robust in aviation
systems is guarding against like cosmic rate bit flips, single event upsets. So simple methods like
CRCs and checksums are sufficient. And also the software that runs it is typically slower and
older, more reliable, and therefore modern data validation methods are... can be very time consuming
for those... for the hardware involved. There's very little code to guard against unexpected scenarios.
If you don't... if it's... if every single line of code costs a hundred dollars approximately,
probably more nowadays than it was when I found that statistic, then you're not going to have a
code for guarding against things that the system designers say won't happen. In fact, as Tim says,
dead code, code that is never expected to be executed, is not allowed in DO-178C.
The... there's a lot of complacency. Because of the level of tests involved, because of the amount
of work that goes into designing the software, there's a lot of point of view in the industry
that the way we do things, the redundancies that we design into the system, protect us from bad
things. And it protects against single event upsets. It doesn't protect against determined
and directed attacks. One thing... one piece of software I was working on a while ago had a... just
a straight-up buffer overflow attack against it. And I had to fight fairly hard to actually get it
fixed, because the incoming data that hit that function with the buffer overflow could only come
from a trusted source that would never send more than such amount of data. And if there was some
sort of, like Aaron says, a single event upset, a sort of random bit flip that caused the length
field to be longer than it was supposed to be, there's a CRC check that would have failed, and
wouldn't have even processed the data at all. So they felt that they were completely protected
against this scenario, because they just don't have this concept of an adversarial attacker with
knowledge of the system being able to get data into this function. They believe that the only
way for data to get into this function is from a source that they trust to not send data that's
going to cause a buffer overflow. So Tim's kind of jumping ahead there. That last bullet point on
this one is software is only tested against expected flight configurations. So you will only
say, here's, you know, this is what we're going to do for this flight, and that's what we're testing,
because testing is expensive. There's a lot of tests that are performed as part of this software
certification process. You don't want to run more than necessary. What that means, though, is that
software, aviation software, while robust in flight configurations, can be extremely brittle
when it is put into conditions that it is not, that are not expected to happen.
Some other things here, ground maintenance devices, so things that actually program
the different flight devices, those are not D1C rated, because they're not flying, right?
They just stay on the ground while the airplane flies. They're covered under some different
guidelines about tool development, but you don't have to go, they're not even
leveling certified, it's something different. Maintenance software, so on each box, there's
typically a component that will help reprogram that device. That's considered to be deactivated,
because when the airplane is in flight, you have a signal that says, are we, are the wheels on the
ground or not? Sometimes it's called weight on wheels, sometimes it's called weight off wheels. Make sure you read your documentation very carefully.
And whatever signal that is, indicates if the, that signal is then used in the startup process
to make sure that the reprogramming software, that component, doesn't run. So this is considered to be
deactivated. There's also frequently a physical switch on the piece of hardware they have to
switch into some sort of boot mode, maintenance mode, programming mode. So you have to not only
have the weight on wheels signal, but you also have to have this switch set in the
activated position to boot the piece of hardware into the maintenance mode. And then the plane
won't fly if that piece of hardware is in its maintenance mode or programming mode. You have to
switch it back to flight mode before the plane will take off. Right, and it'll be like programmed
sometimes that are built into the wiring harnesses themselves. So when you plug in the harness for
reprogramming a box, that thing has a wire jumper in it that forces this type of mode.
So there are some current cybersecurity documents out there, DO-326, which
DO-326, which outlines the activities that should take place at a system and airframe
levels. These are the type of security activities that you should do if you're developing either a
system for an airplane or developing the entire airplane. These are the various testing activities
and testing documents that you should create and how to create them. DO-356 goes a little bit more
into the nuts and bolts of what testing should look like. Something I like about DO-356 is DO-356
does make provisions for the more ad hoc pentest style testing that hackers tend to do. You know,
the adversarial feeling around trying to see, you know, scan different systems, trying to find some
way and some chink in the armor that you can then exploit into the system. This is a testing that's
much... most testing that you see, especially the DO-178C type testing, is extremely formalized.
Every test procedure is written down. You do this set of procedures. This is your test.
That's going to... there's conditions to pass. There's conditions for... and if they don't meet
the passing conditions, the test failed. DO-356 does provide those provisions for the more ad hoc
style testing that can be much more useful for security testing. Provisions for things like
fuzzing, which doesn't really have an analog in like DO-178C, but you can't really formalize a
fuzzing procedure. So that's where we are right now. We've got some concerns with the current
way aviation software is currently defined. What do we do? So what do we do about that? Well,
Tim and I have a plan. First, you know, as with anything, we've got to figure out what our actual
goals are for how to... what needs to be secured, what devices need to be secured, and come up with
some examples, come up with some measures that we can use to reach those goals. It's all very well
and good to say secure the system, but if you don't actually tell people how to go about doing that,
you're going to end up with a large number of ways to do that, some of which may not be very effective.
So the problem is up front here, everything is hackable, right? Give some... give enough access,
motivation, time, and money. You can get into any type of device. You give us a piece of hardware,
and we can get into it. There's a lot of measures you can use to make it more difficult,
but depend... with a large enough playground, you can get into anything you want.
So for goals here, we... so for goals here, we need to assume that attacker has all the necessary
information and resources to do what they want to. If we're going to... if we're going to design
an aircraft to be secure, we need to start from the assumption that the adversary knows
what they need to know to get into it. We need to make sure that we have some way to prove beyond
the most up-to-date way to prove that the software on a particular component is 100% correct. If you
cannot prove that, then it's going to be impossible to figure out how to get to secure an aircraft.
We need to prevent accidental transmission of something malicious. If you know that everything
is secure at some point in time, you need to, you know, protect it from going forward,
and then put multiple barriers in place also to all these different components.
We know that given enough time and money and so on, anybody can get into a device if they want to.
But it is possible to figure out how to prevent, make an attack practically impossible
if you limit some of those things. So if you know when an airplane is on the ground,
that it has all of the correct software and configurations in all of the different parts
that are on the aircraft, then an attacker would have a limited time frame of the actual flight
itself to perform an attack. So that's what we're aiming for.
And also aiming to get the idea into aviation that a software component can go from good
to bad very quickly. Just one exploit and all of a sudden this device that was working completely
fine is now no longer working completely fine. And it's not based on some statistical
degradation over time. Now that can just go be good and then be bad.
So to define what is important to secure, here's my list. We have things that are important for
flying an aircraft. And then we have things that are not important for flying the aircraft.
These are two device categories. The level D-178C defines five different levels
to how critical software is and the consequences of failures here.
For us, there's really only two categories, important or not. Because if you leave something
that has partial measures in place on the aircraft, then that is a potential point that
an attacker could use to pivot to other parts of the aircraft.
So flight devices are any component that's used to operate the aircraft.
Any or any device that communicates with those components. We've seen instances where you have,
you may have a level E hardware device that communicates in some way with even a level A
hardware device. And this is allowed because that communication has been
strictly defined and tested on the piece of hardware, the level A software, to make sure
that it should reject any bad inputs with oftentimes not very robust checking on what
these bad inputs actually are. But from a security context, anywhere that you can touch something
important from, also needs to be secured. Because if you can, you know, have a lower functional,
lower functioning device, lower classification, lower DO1s, then you see a DAL classification
device that can maybe in some way disrupt a higher level, more critical device. And this
is something that you have to think about from the security perspective as an attacker,
using this as a potential pivot to get onto a more critical system.
And also any device or software that interacts with these components, whether in the flight or
on the ground, all your ground maintenance software, is now needs to be considered essentially
from a security level, the same as a flight device. Because these are things that are designed to be
able to modify the behavior of these pieces of hardware that are responsible for
directly controlling the flight of the aircraft. I think that's an important point of what we're
defining here. Things that we consider flight devices includes the things on the ground that
program the device. Because those are very critical to making sure that the correct and
only the correct components are programmed. You know, one thing also, Tim talked about the
different components, different level of components talking together on the same bus.
One very common level A software item on recent aircraft is an operating system
running on a particular device. There is a standard called RX-653, which defines
ways for a partitioned operating system that's effectively like a virtual machine,
can have multiple different severity levels running on the same component.
So as we all know, in security though, virtual machine escapes are definitely a thing. So if
there was an attacker who was able to get into a lower level component, you know that they would
be able to, from there, pivot into the operating system itself, or a more critical component if
they wanted to. So that's our devices. How do we go about doing this? Well, we've got a couple
different things here. So there's adversarial testing. I choose the word adversarial testing
because I don't want to say pentesting, because pentesting means different things to different
people. This is the idea of testing the system as an attacker would. You're no longer just
strictly checking against a specification. You're actually looking at it from, if I'm an attacker,
how could I leverage this system to do something? How could I use this protocol
to do something? All the things that, you know, security professionals that we do in our jobs,
how do we, you know, doing these things to now an airplane?
Another method is some sort of pre-flight software and configuration authentication.
If before every flight there was a way to go and check that the system is actually running
the software that you think is going to be running, actually has a cryptographically
secure method of validating that the software that's running is the software that's supposed
to be running, that your configuration is correct. Other methods could include like
physically incompatible interfaces on flight systems to make sure that no flight system,
you can't just plug your iPad into a critical flight system, that there's the interface on
these flight systems, just, you know, they don't speak these commodity protocols like USB or
Bluetooth or Wi-Fi. We'll talk about this a little bit later. We also need to talk about
air gaps. I know anybody in ICS is definitely laughing a little bit right now, but on an
airplane with a strictly controlled configuration, you know, air gaps could certainly be a part of
the solution for making sure that you can't jump from, you know, the non-flight critical portion
of the aircraft to the flight critical portion of the aircraft, at least as a passenger sitting
in the plane. Now the adversarial testing, you know, review and test all interfaces for
vulnerabilities. You know, you have to, you can't trust, just blindly trust the external
inputs into the system, even if they should only be coming from a system that's also been tested
in the same level and should only be producing correct outputs for you to consume, you still
can't trust this because you can't always trust that the system hasn't been compromised in some way.
I'd like to give an example from automotive for that. If you have one component that tells you
the brake is pressed and you make sure that the thing that actually generates the signal
saying the brake is pressed works perfectly, can't be
cracked, the thing that interprets that signal works perfectly, can't be cracked,
it's all well and good, but if you then have an entertainment system on the same bus
and that sends a message saying the brake is pressed, well, now you can't trust your inputs, can you?
Yeah, and testing your protocol stacks and milestones for vulnerability. I mean, we've
gotten a little bit better, but there's been lots of vulnerabilities found in TCP IP stacks and other
network stacks over the years. Reviewing the software and compile code for vulnerabilities,
making sure you're doing static analysis on the code, not a perfect solution, but it does catch
some things. Secure boot is, I think, a fairly critical part of making sure that we can actually
trust the software running on the systems. Having a good, secure boot platform set up could go a
very long way to preventing at least an attacker from modifying the operating system that should
then be modifying the software that runs on this platform because it should be detected.
And, of course, having multiple layers of protection. Defense in depth has always been
one of the strongest things you can do for the security posture of basically anything.
The topic of secure boot is one that could be talked about for a long time and different people
have different definitions of what secure boot means. At a simple level right now, I think what
we mean is just that there's a way that the hardware has the ability to use cryptographically
secure methods to ensure that only authorized software and components are installed and
operating on that device. And a way to store the keys that should be immutable.
Right. And also, once somebody gets in and pulls apart the hardware that they are not able to go in
and break out, break the secure boot for all of the devices. Right. Something that is,
uses perhaps asymmetric cryptography methods and secure hashing to be used for device.
So pre-flight software authentication, talked about this a little bit earlier.
We want to make sure that the before takeoff that everything on the aircraft is 100% correct
and secure and authentic. So this would be some way, some centralized way to query every single
device and find out what software and configuration are running on them. This is already somewhat
in existing, you know, before an aircraft flies, this is already somewhat what happens, right? We
need to make sure that only the correct software is on each component. So people who fly aircraft
will already have a list of different software versions that should be running on each component
of the aircraft. So this isn't as outlandish as it sounds. You can use cryptographic and secure
algorithms, no CRCs, no checksums. You should be using something like SHA-2, SHA-3, something better.
And there should be also the protocol, the way the centralized device queries every single
component, there should be a challenge response protocol here. The protocol should also be tested
adversarially to make sure there is something that cannot be spoofed. We need to make sure
we can prevent replay attacks. So if there is some malicious software, malicious component on a box,
it should be incapable of falsifying the authenticity of that software.
You can also validate the entire range of memory and flash on each device. You want to make sure
that you can't set the length to zero. You want to make sure that you don't have the correct software
and the correct configuration and put some sort of mystery component in the middle and that
that gap just isn't checked because it wasn't thought to be important, right? You need to
make sure that the entire range is validated. Yeah, physically incompatible interfaces,
you know, we're seeing that like the flight crews, they have the iPad devices that will be there,
their flight book that has the flight information. One of the ways to make sure to, one order to help
prevent malicious software from being loaded onto these flight critical systems is to make sure that
there are physically incompatible interfaces between the non-flight systems and the flight
capable systems. So your flight cable systems shouldn't have USB, they shouldn't have Bluetooth,
they shouldn't have Wi-Fi, they shouldn't have these standardized protocols that everything
speaks, you know, specialized hardwired connections like the connections we have a picture of here,
very common in aerospace, just make it a lot harder for the flight crew to just plug their iPad
into a flight critical system. And if you can see on these connectors, some of the important
parts of them is that they've actually got different keying. So there's usually a bunch
of different, you know, a bunch of different pins so that you have all the necessary signals that
you need for a particular connector. But then you, there's a lot of different varieties of
keying. Some have five slots, some have four, different widths, different positions.
And the whole idea is that you want to make sure that you cannot connect a component wrong.
This is already what's done on an aircraft for connecting all the different flight components.
And this is something that we say is necessary when connecting anything to a flight system.
So air gaps, as Tim said, everybody who's in ICS is probably laughing when we had that out
there before. But the whole point is that an aircraft doesn't change. If it changes,
it changes because the design of the aircraft changes. It changes because there was an actual
documented and, you know, tested reason for doing so. So designing the system,
you should make sure that the flight systems and the non-flight systems cannot talk at all.
They should be physically separate. We, as I said, virtual machine escapes are definitely a thing.
You should not be running on the same box. They should not be able to even talk on the same bus.
So anything that needs, if somebody, you don't want to have to test everything on an aircraft,
right? You want to make sure you can, you want to try and trim what you need to test because
testing is expensive. So something like an entertainment system, maybe somebody doesn't
want to go about testing that. Well, that's okay. If you can make sure that that entertainment
system can never ever talk to a flight system, which means no common buses. It means that the
only thing on the aircraft connected to that entertainment system from the flight components
is power. If you need somebody to, if the crew needs to like disconnect a component, they would
need to be able to, you know, toggle the power to that device instead of actually sending a message
to shut down. So some examples of what we've got here. We're going to go through some different
categories, three different types of systems and talk about how we would apply these things to
ensure that they're secure. Maintenance. In these cover, this is pretty much the, you know, all the
different types of devices that you would have on an aircraft, right? Passenger accessible systems,
things that passengers can get access to and so on. So maintenance devices. These are the things
that program the different components when the aircraft is on the ground. They're usually a fancy
laptop, maybe a robust laptop with some sort of waterproof case and special cables and extra
interfaces to talk to the aircraft parts. These need to be adversarially tested. This is, should
be unsurprising to hear by now. Communications with the different flight devices should require
full authentication and these devices should also have a plan and method to periodically validate
that the device itself has not been compromised. As I said, they're typically a regular laptop
or some sort of PC type device. So any of the standard ways to secure a PC, you know, a laptop
should be used on these devices to make auditing. They should have auditing on, they should have
all the different security protections in place. Programming other devices as well,
as typically it can happen to, there is an ERIN standard for this as well, although it's optional.
Not every device implements it. It's called ERIN 615 for data loading and that can happen over
multiple types of device buses such as ERIN 429. These devices will then usually talk over that.
It's kind of a double-edged sword. On one hand, it means you've got a standard way of doing things.
On the other hand, it means that if somebody implements ERIN 429, you potentially be able
to go up and program with an unauthenticated device, which is why communication with the
flight device should require full back and forth challenge response authentication on both ends.
The device should make sure that the device programming it is who it says it is and vice
versa. Full mutual authentication. That's the term.
So passenger accessible systems should either be incapable of connecting to aircraft systems,
not physically connected in any way, not physically sharing any piece of hardware,
ideally not even speaking the same sort of protocols so they couldn't even accidentally
be connected together. You can't just plug USB into ERIN 429 and have it work.
Or they need to be same as everything else adversarial tested and not have external
connectivity that a normal passenger would be able to just plug into and use. If you have
a USB for charging, it should only be for charging. Only the data lines should be
connected. It shouldn't have any of the... you should be capable of passing data back and forth.
The only case where there's an exception then is if this isn't a system, if the entertainment
system is incapable of being connected to critical flight systems or to flight systems,
then you could have a USB audio interface on it.
Yes.
But that's the only case where that would be allowed. You would need to make sure that this
device cannot talk to anything else. And the whole goal here is to make sure that something
can't be done, something cannot accidentally or through somebody dropping a bad cable somewhere
near the airport, have somebody connect something that shouldn't be connected to the flight systems.
That's the whole goal here. If somebody is going to try and attack an aircraft
during that small, that limited window of the flight itself, we want to make sure
that it is incredibly obvious that they're doing something that they shouldn't be doing.
So just plugging the USB in is very benign. But if they're starting to rip up panels and trying
to find the 429 bus somewhere down there, well, that should hopefully be obvious to
some of the other passengers or the crew and corrective measures could take place.
But that's the whole goal here. We want to make sure that it can't be done accidentally
or on purpose without it being obvious.
So the flight systems, the flight systems themselves, we've talked about these
quite a bit already. These need to be adversarially tested, of course. We need
to make sure that there's multiple levels of... there's multiple layers of protection
in the way for anybody who is trying to attack a system that they would need to get through.
No consumer interfaces. So all those flight systems, you need to make sure that you do not
have the... you don't have the... you know, there's no USB in there. There's no Wi-Fi in there.
So iPads as a flight bag are a thing now. And obviously, there's an appeal in terms of
how easy it is to update. You don't have to carry around stacks and stacks of paper.
There's... it's an easy way to store a lot of things.
But that means you've now got a device which is in the cockpit, which is considered a flight
critical system, which is a consumer device. And that gives me some concerns. So I think
there needs to be some thought on how to secure that type of system. Maybe it just needs to be
not an iPad. Maybe it can be a special purpose device. There's plenty of things out there with
LCD. They can store maps and have a program in them. No consumer interfaces. Yeah, so no USB.
You wouldn't be able to connect this. You don't want to have somebody accidentally plug in a USB
as you're not supposed to, right? So just as a quick summary here. Again, our goals.
These are the things that we want to achieve. And I think we have for what we've put
in place. Making sure we still have to assume, again, that's up front. An attacker has everything,
knows everything. We've talked about providing a way to make sure that the systems can be validated
to be correct. That the software and configurations on the different components are correct
when the aircraft, before the aircraft takes off. We want to limit that potential attack window.
We've talked about the ways we can prevent accidental transmission of something malicious
to the physical air gaps, physical disconnects, physical incompatible interfaces.
And then, again, if this is all, the goal is to make multiple barriers there.
Multiple barriers there an attacker would need to get through.
Yeah, and then two device categories. There's stuff that can affect flight and stuff that can't
affect flight. And can't affect flight does, in this case, mean physical, full physical isolation
of anything flight critical.
Methods. We've talked about these at length. Adversarial testing, I believe, is a big key part
of this. One thing I guess we didn't really talk about is kind of design standards. It's something
that could be addressed as well. Making sure that the software as it's developed complies with
the different best practice recommendation of how to develop secure software in terms of
functions that are allowed and such. That's another potential method. We are more looking
at the fitting things on top of what was there already. But we still do have a few problems
that we need to solve. We're not going to try and pretend that we solved everything here.
We'd like to think that we solved a significant part of aviation cybersecurity just in this talk.
But there's a few things that we need to think about going forward. Supply chain security is
still a concern. Obviously, as I said, anything can be hacked. As the devices are sitting in
storage, an attacker could go in and modify them. They've got plenty of time to go in and modify
them, figure out how they work. Either modify the software or just physically. Physical
modifications to the hardware. And how to make sure that that doesn't happen or can't happen
is a challenge. RF communication is also another area that we can't really address. The airplane
has a fair bit of RF communication. It has radio, ADS-B, weather, etc. This is also something that
wasn't addressed by what we've presented here in this talk. The flight crew, the pilot's training
is a significant part of that. If there's issues with communication between the aircraft and ground,
that's something where training can kick in and deal with the situation. But it is still
something that would improve matters if there was a way to secure the communications.
Things that we might also want to think about in the future are how often, how much change
would require something to be retested, more adversarial testing. What level of change,
where different amounts of change are considered to be minor fixes, and they don't have to require
a complete redesign of the system. But some level of change does require a complete redesign and
retesting the system. So that's something that would need to be looked at in the future.
And then there's also the maintenance devices themselves. We talked about how
maintenance devices are used to program all the different components on an aircraft.
This means that would be used to program both flight systems and these air-gapped non-flight
systems. So maybe those need to have a slightly different category. You could
argue, you can put together a committee meeting and argue about lots of this stuff for a while
if you want to. But I think that what we've given here is a fairly complete approach
to address cyber security. Any questions? We'll be in the discord for any questions.