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The title pretty much says it all. I'm wondering if it is possible through "digital" means only (aka any physical disruption of satellites is not allowed) to disable the US GPS satellite constellation. Here are some additional details to help with answering:

  1. This would require that the GPS satellites have receivers that accept commands in some form. I'm guessing that such a setup is not necessary - technically all the satellites have to do is station keeping and signal broadcasting. I'm sure they could be completely automated and therefore may not have any remote control possibilities at all, making this impossible.
  2. However, I presume that they have some basic capabilities for two way communication to assist in the event of a malfunction, so that the satellite may be returned to service without a very expensive replacement. This part of the satellites is what I would be targeting.
  3. I presume that the satellites are not linked to each other in any way, and therefore disabling the network would require attacking each satellite individually
  4. I understand that the United States is not the only country that operates a global positioning system, and therefore that bringing down the US GPS system will not immediately disable all GPS devices globally. However, I am making the (rather narcissistic) assumption that the US system is supported by the majority of devices world-wide.

Therefore, a particularly helpful answer might aim to address these particular items:

  1. Do the GPS satellites even have the receiving capabilities that are a minimum requirement to make hacking even remotely feasible?
  2. Any information about the communication channels used for managing these (or similar) satellites and details about the software on the satellites, would earn extra bonus points! I presume many details are Top Secret in real life, so I'll accept anything that shows that such an attack may be plausible, even if it may not actually be possible.
  3. Presuming that hacking the satellites is not outright impossible, what level of resources would an attacker need to manage it simultaneously on a global scale? "Simultaneous" probably isn't realistic, so to pick a hard target, let's say that I want to get enough satellites "down" in 24 hours to make all consumer-grade GPS devices useless.

Please help me accomplish my evil goals! If the GPS on your phone stops working next month it's not my fault.

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    $\begingroup$ "If the GPS on your phone stops working next month it's not my fault." OK, @conman, I believe you. Wa-a-a-it... $\endgroup$ – VLAZ May 22 at 17:23
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    $\begingroup$ If you think a moment about this question, the answer is certainly "yes" because satellites require maintenance and that means they all have remote access from Earth - but only someone desperate to be arrested by U.S. Homeland Security or Interpol would dare explain how. Please tell us you're not asking how to do it. (And if you're not, what are you really asking?) $\endgroup$ – JBH May 22 at 17:41
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    $\begingroup$ BTW, I was serious about that last comment. No one in their right mind would explain how to do it on a public website. The dark web, maybe... but not an open website. $\endgroup$ – JBH May 22 at 17:48
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    $\begingroup$ @JBH I'm certainly not asking how to do it (any knows certainly wouldn't post it here). I'm only asking if it is possible. It seemed likely that the satellite constellation has remote control options, but I didn't know that for sure, or whether or not those would allow actual changes to the systems or simply diagnostic information. Further, I wasn't sure if such an attack would be realistic regardless - coordinating a world wide attack is usually only feasible in movies, and I hate movies where the bad guy lives in his basement but has limitless resources. $\endgroup$ – conman May 22 at 17:50
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    $\begingroup$ @JBH Certainly! You'd have to be an idiot to post something like that here, and someone that foolish is unlikely to be in a place where they could learn how to do it. $\endgroup$ – conman May 22 at 17:51
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GPS satellites - almost all satellites, really - need to have the capacity to be remotely "disabled" as part of their end-of-life protocol. Satellites degrade over time like all things do (especially things exposed to the orbital environment) and they're also steadily rendered obsolete. To avoid old satellites cluttering up the most useful orbits and becoming a navigational hazard for their successors, satellites are normally boosted upwards into a graveyard orbit (an orbit nobody is actively using, where it can drift in peace) or downward into a disposal orbit (where the satellite will eventually deorbit and disintegrate in the atmosphere). They will also be passivated, removing volatiles like propellant and power storage to minimize the risks of a future collision.

Given the operating parameters of satellites, end-of-life is a one-way trip. Once it begins its graveyard or disposal burn, it won't have sufficient fuel to return to its intended orbit, and once it's passivated, it literally lacks the motive power to be able to restore itself. All your hackers have to do is convincingly mimic signals from the ground controller telling the GPS network to retire itself, and it will be irreparable. As a bonus, since satellites EOL at different times, you could retire satellites one by one to prove you're serious.

According to their Orbital Debris Mitigation Standard Practices (pdf) the US government requires end-of-life disposal for all missions, whether civilian or military. I don't know what methods GPS satellites specifically use, or if they were exempted for some reason.

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  • $\begingroup$ I like this! I imagine that bricking the satellites may be impossible, and depending on the setup any malicious changes may be reversible. However, if you manage to initiate the EOL procedures, there is literally no coming back. $\endgroup$ – conman May 22 at 19:02
  • $\begingroup$ Would EOL procedures make the satellites immediately irrecoverable though? It would probably take some time for them to burn enough fuel that they couldn't get back. It's not like they're setting off a big rocket. $\endgroup$ – Harabeck May 23 at 14:14
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    $\begingroup$ @Harabeck I don't imagine a satellite would have much fuel, at least compared to what a continuous burn would use... It wouldn't be instant, but it isn't implausible that mere minutes might be enough to empty its fuel storage? $\endgroup$ – Yakk May 23 at 14:31
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    $\begingroup$ @Yakk That's not clear to me. A space stack exchange question led me to a calendar of outages caused by corrective maneuvers, and those seem to last 1-3 minutes and have to be done every year or so. My best guess is that they have small slow thrusters that would take hours to get them into a proper EOL orbit, and so the operators would probably have several minutes at least to notice the problem and correct. space.stackexchange.com/questions/30752/… $\endgroup$ – Harabeck May 23 at 15:42
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    $\begingroup$ @Phlucious: Not if you turn off the receiving antenna. $\endgroup$ – Joshua May 23 at 20:22
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This is from the Wikipedia entry for GPS, regarding its control segment:

The flight paths of the satellites are tracked by dedicated U.S. Air Force monitoring stations in Hawaii, Kwajalein Atoll, Ascension Island, Diego Garcia, Colorado Springs, Colorado and Cape Canaveral, along with shared NGA monitor stations operated in England, Argentina, Ecuador, Bahrain, Australia and Washington DC. The tracking information is sent to the Air Force Space Command MCS at Schriever Air Force Base 25 km (16 mi) ESE of Colorado Springs, which is operated by the 2nd Space Operations Squadron (2 SOPS) of the U.S. Air Force. Then 2 SOPS contacts each GPS satellite regularly with a navigational update using dedicated or shared (AFSCN) ground antennas (GPS dedicated ground antennas are located at Kwajalein, Ascension Island, Diego Garcia, and Cape Canaveral). These updates synchronize the atomic clocks on board the satellites to within a few nanoseconds of each other, and adjust the ephemeris of each satellite's internal orbital model. The updates are created by a Kalman filter that uses inputs from the ground monitoring stations, space weather information, and various other inputs.

Satellite maneuvers are not precise by GPS standards—so to change a satellite's orbit, the satellite must be marked unhealthy, so receivers don't use it. After the satellite maneuver, engineers track the new orbit from the ground, upload the new ephemeris, and mark the satellite healthy again.

So all you need is access to a GPS engineer's workstation (which can maybe be obtained remotely) and someone's login (so many ways to get one) and you can start spreading chaos. Merely changing a few satellites' datetime to random values will cause the system to stop working until someone fixes it.


You may be wondering how secure the air force base must be. Consider that GPS security is probably less critical for world safety than intercontinental nuke security. Consider the baseline for the security of those things (it's a miracle we're not all dead by now). You might be able to sneak in with a pizza box and a pizza delivery uniform.

It may be that the GPS operation console runs on floppies just like the nuke consoles do. If so, switch the GPS floppies with malicious ones and see as the operstors upload bad instructions to the satellites.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – L.Dutch - Reinstate Monica May 23 at 6:07
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    $\begingroup$ I would argue that this is not so simple. GPS is a US Air Force-owned system. The US military depends on it. Pulling this off would require getting through all of the security systems, both physical and digital. There is almost certainly no remote login to the GPS control terminals. Even a large nation would have a hard time disabling GPS in this way. $\endgroup$ – BillThePlatypus May 23 at 10:56
  • $\begingroup$ @BillThePlatypus I am editing the post to address that, since previous comments were moved to chat. $\endgroup$ – Renan May 23 at 11:41
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    $\begingroup$ You could not get to a GPS terminal on a US air force base with a pizza box and a pizza uniform. You would definitely need a CAC card or someone with a CAC card to let you in and then you would need a CAC card to log on. Someone could violate federal law and log you on with their CAC card if no one else were around to stop them, but that would require a lot more social engineering than a fake pizza delivery. You could steal a CAC and socially engineer the PIN. Again, if no one at all sees you getting in and the CAC isn't disabled in a timely fashion, that might be the best bet. $\endgroup$ – Todd Wilcox May 23 at 18:23
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GPS transmissions come to Earth very attenuated, and hence are very sensitive to jamming (radio blabbering) and spoofing (fake messages impersonating sattelites). A radio station switched to the appropriate frequency would deny a large area.

The catch is that it automatically broadcasts the jamming source location. A missile could literally lock on to the jamming signal.

Luckily, we're all carrying small radio transmitters. A sufficiently successful mass-deployed cell phone virus could turn all infected devices into jammers or spoofers, effectively denying GPS in all populated areas. Be warned that there may be extra safeguards against changing the radio frequency, so owning the Operating System may not be enough and the solution will change with cell phone models. On the other hand, you don't need to cover all models.

To cover unpopulated areas such as oceans, you'd need a massive drone army.

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    $\begingroup$ This is exactly what I was going to post, and I'm surprised no one else mentioned it. Don't forget about spoofing, too. Both jamming and spoofing occur regularly, though mostly in military testing. You could also simply overwhelm the GPS signal with a stronger signal on the same frequency... there was a huge lawsuit a couple years ago when LightSquared acquired an adjacent frequency that might have interfered with the relatively weak GPS signal. $\endgroup$ – Phlucious May 23 at 15:26
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    $\begingroup$ Jamming would work, but you can't do it using cell phones. None of the frequency bands are anywhere near the GPS frequencies. $\endgroup$ – Mark May 23 at 21:47
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Certainly -- if you're the United States Government.

They temporarily turned off the "dithering" of the system at various times (including during the first Gulf War, due to shortage of mil-spec GPS devices) and did so permanently in the late 1990s (I don't recall the exact year, and it doesn't really matter here). They could, in theory, turn it back on at any time, limiting civilian GPS accuracy to around 50 meters error as it was originally.

Or, they could ("temporarily") turn the entire system off, if there were a situation that made it seem like a good idea (say, advance notice of a bunch of GPS-guided Bad Things being launched at American targets).

Now, given that it's possible for the folks who built and operate the system, I'd say it's very much possible for sufficiently skilled and motivated hackers to gain access to the control systems and either disable the entire system, or disrupt it enough that (at least for a while) it's more dangerous to use it than to ignore it (say, for holding course in an airliner on a trans-Polar flight).

As with information on how to build a nuclear bomb, it's probably best to hide the details of exactly how it would be done -- write it as a "hacking" scene the way other novels and movies generally do.

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    $\begingroup$ Interesting. I'm sure the answer to this isn't known but I'll ask anyway: Does that suggest that the easiest way to do this wouldn't be to interact with the satellites directly using "my" infrastructure, but rather to hack into whatever systems the government uses to control the satellites and just use that? Any chance there is a single control point or would it take world-wide effort? Obviously in the end the answer will be whatever the story needs it to be, but I like to aim for realism. $\endgroup$ – conman May 22 at 17:39
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    $\begingroup$ For the Ameican GPS system, as I understand it (as a casual end user only), there's what amounts to a central control that turns certain features of the system on and off as a whole. If you wanted to deorbit a particular satellite, or move it to "storage" and put another in its slot, you'd do that individually, but for things like dither and full disable, my understanding is you don't have to individually switch hundreds of birds. $\endgroup$ – Zeiss Ikon May 22 at 17:48
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    $\begingroup$ Selective availability hardware and capability ("dithering") has been removed from the latest generation of GPS satellites specifically to provide assurance that they cannot turn it back on. $\endgroup$ – user71659 May 22 at 21:07
  • $\begingroup$ @user71659 Well, that's inconvenient -- if you want to disrupt airline and auto traffic on a worldwide basis, anyway. The controls to turn the whole thing off, or "park" or deorbit the satellites still exist, however. $\endgroup$ – Zeiss Ikon May 23 at 11:16
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"Maybe":

GPS, and the other services, satellites contain communications and state control interfaces because they are designed to be able to be controlled from ground stations.

One of the key functionalities of those state controls are what level of encryption is used to broadcast their signals - the US's GPS is first and foremost a military service, that was opened up to civilian use as a secondary functionality to gain more usage out of the expense of putting them in orbit.

During times of war the network can be modified to revoke that open civil usage and rely on more heavily encrypted signals that only official military receiver units would be able to use or understand.


So we clearly have vectors to carry out various attacks, with multiple options to the "end result" of the attack.

  • Limit or remove Civil Use
  • Disrupt official military use with a more complex attack
  • Potentially destroy the array entirely by placing all/most satellites in unrecoverable modes and require physical replacements or repair.

As far as carrying out the attack, that would require a very complex and skill/resource intensive operation. [Possibly made far easier with advanced insider knowledge. As with any computer system, there is potentially a shockingly trivial exploit that has been overlooked]

Simply flipping modes to restrict Civil usage [the majority of GPS units/receivers] would likely be detected and corrected in minutes, but repeated attacks may take some time to completely correct and prevent being disrupted over and over again. [Maintaining spotty GPS with it flipping on and off for a full 24 hours like this might be stretching it]

An exploit to attack each satellite's station keeping systems probably has the highest potential to bring the system down and keep it from being restored in minutes.

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    $\begingroup$ Needless to say - putting all those satellites to space was pretty expensive. Bricking them would be ... kinda rude, to put it nicely. And slamming them into other satellites to trigger a Kessler syndrome would be even ruder. $\endgroup$ – John Dvorak May 22 at 17:50
  • $\begingroup$ Yes, the most likely options for such an attack that would last more than a few minutes/seconds is probably not something that falls under the realm of 'white hat' hacking... $\endgroup$ – TheLuckless May 22 at 17:52
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    $\begingroup$ @JohnDvorak ruder? More rude? Rudable (capable of being rude)? Rudless (lacking the quality of being rude)? I love English.... $\endgroup$ – JBH May 22 at 17:55
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    $\begingroup$ @TheLuckless lol! I'm pretty sure that making any changes all, even if quickly fixable, probably would not fall under the label of "white hack" and probably will get you arrested, with prejudice, very quickly. Next question: if I attempt to hack the GPS system, just how quickly will I get arrested? That is probably best answered by experimentation. Any volunteers? Not it! $\endgroup$ – conman May 22 at 18:12
  • $\begingroup$ "During times of war the network can be modified to revoke that open civil usage and rely on more heavily encrypted signals that only official military receiver units" Only on the latest receivers. Older military receivers require the civilian signal to synchronize, hence the name Coarse/Acquisition code. It was designed this way because the entire signal was originally meant to be classified; civilian use came later. $\endgroup$ – user71659 May 22 at 21:12
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All GPS satellites have two-way ground communications, they need semi-continuous (the longest maximum no check-in time is measured in months) ground telemetry updates. You wouldn't need to hack the satellites, individually or collectively, you'd just need to corrupt that data and crash everything. By which I mean literally crash it, hot metal falling from the sky and no more GPS until new satellites can be launched. There are at least two major obstacles to this approach, first you have to hack the US Air Force's 50th Space Wing to plant the bad data, that will not be an easy mission. The second barrier may be even higher; you have to get all 8 separate blocks of satellites all with different programming, design specifications and check-in schedules to request and upload that bad data within a window of only a few minutes because as soon as the first satellite hits atmosphere someone will almost certainly start to make manual corrections.

So can you do it? Maybe. But It would require good timing and/or a very rare timing interface event that could be exploited and you'd really need to disable ongoing communication afterwards or timely intervention by ground control is going to mess you up.

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  • $\begingroup$ I assume the satellites don't try to automatically correct their orbits, unless specifically commanded to. $\endgroup$ – user253751 May 22 at 23:35
  • $\begingroup$ @immibis They will but that's why you hack the telemetry, you are telling them they're out of alignment and need to "correct", right into the atmosphere. $\endgroup$ – Ash Jun 2 at 17:20
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Okay, so they can in theory be hacked. That's already been explored enough there is no need to delve any deeper, but they are one of the world's most secure networks because they are intrinsically so simple. They only need to accept a few commands such that securing all of your vectors of attack is much easier than most systems you'll otherwise encounter.

That said, there are ways to mess with a GPS network that don't involve directly hacking it. During operation desert shield, Iraqi e-warfare specialist found that they could not decrypt GPS signals to feed the false data they wanted, but they could recorded the encrypted transmission, and replay it later to fool American Aircraft into crashing by making guidance systems believe satellites were in the wrong spot at the wrong time. I doubt military grade systems still suffer from this limitation, but I would not be surprised if a number of civilian devices could still be fooled in this way.

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