Jammer in the works

27 July 2021

Global navigation satellite systems like the US’s Global Positioning System have become deeply embedded in both the function of modern militaries and society as a whole. However, this dependency could leave the technology vulnerable to exploitation. Nicholas Kenny speaks to Alexandra Stickings, associate fellow at the Royal United Services Institute, and Elisabeth Braw, resident fellow at the American Enterprise Institute, about the growing threat of jamming and spoofing.

In January 1991, the US and its allies launched Operation Desert Storm in response to the Iraqi invasion and occupation of Kuwait, sparking the conflict that would become known as the Gulf War. The weeks-long air offensive, while devastating for the Iraqi army, was not sufficient on its own to drive Saddam Hussein’s forces out of the country. The coalition needed to launch a ground campaign to end the war, but it faced a number of challenges when this began on 24 February 1991. The speed of warfare had changed – US Army artillery had historically required a day or so to survey its targets and set up munitions, but the speed at which its opponent’s armoured tanks, trucks and other vehicles moved at meant that artillery guns would need to be set up, fired and redirected far more swiftly.

The Pentagon hoped that the Global Positioning System (GPS), at that point untested in war, would provide the solution to this problem. However, the system it had at the time was far more rudimentary than the version currently in use. Accuracy fell within about 16m, rather than the to-the-centimetre precision possible today. Despite this, GPS was cited as a key element in the success of the ground war – which lasted only about 100 hours – aiding hugely with land navigation and artillery support.

“If you look back to the first Gulf War in the early ’90s, it’s often referred to as the first ‘space war’, or ‘space-enabled war’, because that was where we saw GPS really being used,” says Alexandra Stickings, associate fellow at the Royal United Services Institute (RUSI). More than that, though, the Gulf War demonstrated the value of GPS in military systems. Modern air forces now use GPS for navigation, target tracking and reconnaissance, and it has become an integral part of how they operate. However, therein lies the key danger: unlike many technologies used for military purposes, GPS is dangerous in part due to its invisibility. “It’s become so ubiquitous,” Stickings explains. “So many aspects of our daily lives use this technology. And because it’s so widespread, it’s not at the forefront of people’s minds – when you have something that is reliable and is just in the background, we don’t always see it.”

Elisabeth Braw, resident fellow at the American Enterprise Institute, calls this “the convenience trap”. As she sees it, society’s relationship with technology since the dawn of time has been in the service of greater and greater convenience. However, this comes with a cost – in the case of GPS, our reliance on the functionality it provides has resulted in some troubling vulnerabilities.

GPS is made up of three components – satellites, receivers and ground control stations. GPS satellite signals carry a time code kept by incredibly accurate atomic clocks, which are synchronised with each other and with counterparts on Earth. The clocks enable each of the 31 GPS satellites operated by the US Space Force to continuously broadcast a signal that includes the time and the satellite’s predicted position. GPS receivers – whether they are installed on ships or as part of a smartphone – work out their latitude, longitude and altitude by measuring the relative time delay of signals broadcast by a minimum of four satellites.

Today, GPS – and other global navigation satellite systems (GNSSs), such as the EU’s Galileo constellation – is used for everything from pizza delivery and earthquake measurements to automated vehicles and missile and projectile guidance. Efforts have been made to keep military and civilian GNSS systems separate – Galileo, for example, has two signals. One is for general use, while the public regulated service (PRS) used by militaries and emergency services is designed to be more resistant to attack. However, the overlap of military and civilian systems has inevitably caused friction. And, as GPS and navigational satellite systems have become embedded in military operations, adversaries have become increasingly intent on tampering with them, Braw explains. “Yes, the military always – in every area – uses more secure technology than the rest of us. But no technology is ever completely secure,” she says.

Attack the signal

As the use of GPS for military operations has increased, so too has the development of anti-GPS technology. This typically takes two main forms – jamming and spoofing. Russia and its proxies have proven to be particularly adept and eager with jamming GPS signals, which has led to an increasing awareness of its vulnerabilities among the Nato member states.

GPS jamming operates by targeting the receivers, producing a radio frequency signal strong enough to drown out satellite transmissions. The user will immediately be able to detect such an attack, whether deliberate or accidental, as the information the receiver is supposed to pick up will no longer be available. This can lead to serious disruption, as seen in 2016 when South Korea was subjected to a major campaign of GPS jamming from North Korea, which affected ship and aircraft navigation. One of the main threats with jamming, Stickings notes, is that the perpetrators “don’t have to be a space actor to be able to interfere with space systems – [jammers] are fairly easy to come by”. Jammers are so readily available that they’re sometimes used by London taxi drivers to avoid the rules on maximum driving hours or to prevent their employers from tracking them. In 2013, Newark Airport’s air traffic management operations were regularly affected by a man whose commute took him past the airport – he was also using a jammer to stop his employers from tracking him.

GPS spoofing, on the other hand, is “more of a cyber capability,” Stickings says. Sometimes called ‘denial-of-service’ spoofing, it involves deliberately mimicking the form of transmissions from GPS satellites, thereby tricking the receiver into believing that it has been sent information as expected.

“The idea with that is, for example, for navigation purposes, you’re not where you think you are, because you’re receiving a signal that’s actually incorrect,” she adds. “Or a precision-guided munition might not go where it’s intended to go. This is obviously more difficult [than jamming], because you have to create a signal that’s not easy to distinguish as being fake.”

Such an event occurred in June 2017 in the Black Sea, when more than 20 ships operating near the Russian port of Novorossiysk realised that their satellite navigational systems placed them 32km inland, at Gelendzhik Airport. While not confirmed, experts at the time believed this to be the first documented use of GPS misdirection. The danger this can present comes down to international borders and territorial waters. An aircraft patrolling the edges of a border could be spoofed into accidentally crossing over and becoming an intruder – this can be particularly dangerous in contested areas, where such an incursion could serve as the pretext to violence.

Star wars

While jamming and spoofing both involve interfering with the receiver, satellites themselves could also become vulnerable to attack. A number of nations now boast anti-satellite missile capabilities, but Stickings sees this serving as more of a deterrent than something that will receive widespread use.

“Destroying a satellite kinetically creates a huge amount of debris, which is particularly a problem in low-Earth orbit,” she explains. “It’s not in anyone’s interest to increase debris – there’s a fairly fine balance in space at the moment between the major powers and other users. I think that sort of activity would not happen until much later on in a conflict – certainly not in terms of first or second-strike capability.”


GPS satellites operated by the US Space Force, which continuously transmit signals containing time and location information

US Space Force

There’s the rub – unlike jamming and spoofing, a kinetic attack is much harder to hide behind plausible deniability and, therefore, is more likely to invite a direct response and possibly lead to escalation. However, there are other issues beyond deniability.

“If we look at low-Earth orbit – where kinetic antisatellite missiles are more likely to be deployed – there are many, many satellites,” Stickings explains. “If you have a constellation of 200 satellites that are linked, destroying one probably won’t affect the capability very much. So, in that sense, you start to think, ‘kinetic anti-satellite missiles are very expensive, but these satellites can be very cheap’.”

Civilian fallout

The real conflict in space, then, has been more about the denial and disruption of space assets and information rather than their destruction. That’s not to say, however, that these technologies don’t cause damage back on earth or in the air. While military GPS operations are heavily protected, civilian ones are often less so – and, when they overlap, there can be serious ramifications for the civilian populace, even when unintended. In July 2019, Ben Gurion Airport in Israel experienced a massive GPS-denial attack, which affected the country’s civil aviation sector for the three weeks. The exact cause remains unconfirmed, but Israeli experts pointed to a possible spillover from Russian forces in Syria, which were making heavy use of GPS jamming technology. As GPS continues to play an integral role in our society, the likelihood of similar unintended attacks can only grow.

Stickings points out that part of problem here is GPS offers little distinction between a guest in a warzone or an active player – making it part of a so-called “grey zone activity”. Much of Russia and China’s current activity operates in this domain, she says. “It is a constant competition in that sub-threshold area. I think, in that sense, GPS jamming is going to become more common. Because of its potential range, it can have those spillover effects, which has consequences in terms of economic loss and the impact on other areas of civilian life.”

However, it’s not just Russia and China that are running these kinds of operations. Militaries in the West also make use of jamming and spoofing technologies, and it is all too easy for what seems like a targeted strike on an opponent’s satellite navigations to have an unintended affect on the population. “That is the risk, both for civilian and military organisations,” Braw notes. “And as we know – in today’s geopolitical climate – a civilian entity can be targeted as part of a geopolitical dispute or to launch [one], so that the two are not separate in the way they used to be.”

Whether or not civilians are intentionally targeted by anti-GPS technology, the fallout raises the same questions. “We’ve seen organisations like the Red Cross start to become engaged in some of these conversations and around cyber as well,” says Stickings. “On how military operations employ [anti- GPS] capabilities, which could have spillover effects on civilians. And the extent to which a military can be held responsible for damage to civilian economies or civilian operations, particularly where there could be issues around a humanitarian crisis, for example.”

So, then, what is the solution? Militaries have already been hard at work encrypting and protecting their GNSS signals and receivers, making it more difficult to interfere with them. Similarly, some are working on back-up systems, in the unlikely event that the network they use would fail entirely. At the same time, many have started holding training exercises in the case of a GPS-denied environment.

“What they’re doing is essentially returning to manual skills as a backup,” says Braw, noting that celestial navigation has been around for thousands of years, and offers the benefit of being more secure than satellite technology ever could be. “I think it’s sort of endearing that the human brain, with very simple instruments, can be essentially unbeatable in a way that the best technology is not. Yes, it’s not as precise, but the other side can’t interfere with it.”

Just as the Gulf War had demonstrated the change in the speed of warfare, we’re also learning to see the benefits of the slower human mind, too. While GPS will remain an integral and invaluable part of air force and military operations – and society at large – convenience can all too easily become a crutch if it is relied on too heavily.


Ships were affected by possible GPS spoofing near the Russian port of Novorossiysk in June 2017. 

New Scientist

Disruption to satellite navigation signals at Ben Gurion Airport in Israel in 2019 was reportedly caused by GPS jamming.

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