What's the Difference Between GPS Spoofing and Jamming?

What's the Difference Between GPS Spoofing and Jamming?
What's the Difference Between GPS Spoofing and Jamming?

In recent years, satellite-based positioning has spread to nearly every industry and is present in products that people use heavily every day. The global positioning system, or GPS, has transformed vehicles, sports watches, the stock exchange and our smartphones. GPS is an invaluable resource for locating objects geospatially or synchronizing them to one clock.

GPS is a satellite system made up of six orbital planes centered around Earth, each of which contains four satellites. GPS was not available for civilian use until 1983, but since then, products and systems that operate on GPS have become nearly ubiquitous. With this extreme popularity and utility, GPS has attracted malicious actors who exploit the system for personal gain or even military operations. It has become clear that GPS is vulnerable to attack, with two primary forms of interference: spoofing and jamming. Understanding these attacks is essential to securing GPS and preventing exploitation.

GPS Spoofing — an Overview

GPS spoofing is the term given to attacks in which hackers transmit GPS-like signals and code them in a way that tricks receivers into thinking they are in a different location than they are. Someone conducting a spoofing attack is trying to lie to a GPS receiver through the broadcast of incorrect signals disguised as typical ones. It's also possible to conduct a spoofing attack by broadcasting genuine signals with the wrong timestamp, or signals captured at a different location. The spoofer then modifies these signals to make the receiver believe its position is in a different location, or in the right place at the wrong time.

Carry-Off Attacks

One of the most common types of GPS spoofing attack is called a "carry-off" attack. This type begins with the attacker broadcasting signals that sync perfectly with the target receiver's legitimate signals. The attacker then gradually increases the power of the signal until it essentially drowns out the genuine one, causing the receiver to track the false signal instead. At that point, the attacker can manipulate the signal so the receiver reports a different location or time than the real one. The goal of carry-off attacks is to evade detection, making them primarily the domain of military operations.


Meaconing is a less technology- and equipment-intensive form of attack than a carry-off. In this form of GPS spoofing, the signals get re-transmitted, rather than altered. GPS repeaters are often the source of meaconing, whether intentional or not. An example of a repeater is the equipment found in airport hangars that allows the detection of GPS signals indoors, usually for testing. If someone increases the power of one of these repeaters — accidentally or on purpose — the result will be the broadcast of an incorrect signal.

Examples of GPS Spoofing

GPS spoofing is typically a military effort rather than a civilian operation, and there is a disturbingly large pool of known cases. C4ADS, a research group from Washington, D.C., has published a report on spoofing of the Global Navigation Satellite System (GNSS) by Russia. The report found that Russia interfered with navigation on more than 1,300 civilian vessels over almost 10,000 interference attempts. These vessels were near Russia, Syria and Ukraine.

The International Civil Aviation Organization released a report in 2019 indicating that there were 65 spoofing incidents across the Middle East in the preceding two years, while Eurocontrol received more than 800 reports of GNSS interference in Europe in just the first half of 2018. GPS spoofing is an area of growing concern for governments around the world.

What Is GPS Jamming?

GPS jamming refers to the act of utilizing a frequency transmitting device to interfere or block communication such as text messages and phone calls. While GPS spoofing is primarily the work of military operations, GPS jamming is something anyone can do with relative ease. A jammer is a device that confuses the receiver by emitting radio signals at the same frequency as the GPS. This interference hampers the ability of the GPS device to determine its correct position.

A GPS jamming unit is generally small and self-contained, so the user can readily transport and hide it. The device typically sends out a signal of 1575.42 or 1227.60 MHz. This signal then gets broadcast over a radius of five to 10 meters.

Up until recently, these jammers would draw power from the cigarette lighter in a vehicle, although today's users typically plug them into a vehicle's USB port. The jammer needs to be very close to the GPS tracker to work, which is why most people use them to thwart tracking devices installed in vehicles by employers. Jammers are prompt to start up and are usually ready to operate in just a few seconds. They also use relatively little power. That makes them easy to turn on when needed and switch off quickly to avoid detection. What's more, these devices are readily available online for prices nearly anyone can afford.

The danger of such devices is obvious, and jammers are against the law in the majority of developed nations. In the U.S., it is illegal to use, sell or even market jammers, with fines reaching into the tens of thousands of dollars and the possibility of jail time as a consequence. However, because someone using a jammer can unplug it in a matter of seconds, it is difficult to catch them in the act.

Examples of GPS Jamming

People most frequently use cigarette-lighter or USB jammers when they don't want their employers to track their movements with onboard GPS. Delivery and truck drivers are common examples. In 2013, the Federal Communications Commission fined a New Jersey man almost $32,000 after catching him with a GPS jamming device in his truck, which he was using to hide his location from his employer.

The man got caught because the signals he was using to disguise his whereabouts were blocking reception of GPS signals by the Newark Airport. By disrupting satellite signals, he was damaging air traffic controllers' ability to get accurate information on plane locations in the air as well as on the runway, causing chaos every time he passed the airport.

Although jamming is more of a civilian activity, it has occurred in the military sphere as well. In 2015, the Department of Homeland Security confirmed that drug cartels were spoofing and jamming the drones used for U.S.-Mexico border surveillance.

GPS Spoofing vs. Jamming — What's the Main Difference?

While they may cause some similar fallout, spoofing and jamming are two very different processes. Spoofing requires the attacker to be able to recreate signals from more than one satellite and transmit them to a specifically targeted receiver. As long as the targeted receiver can't tell the difference between the legitimate signals and the spoofed ones, the attack may go unnoticed.

Coordinating and carrying out a spoofing attack is a lot more complicated than jamming GPS, especially in an intentionally covert scenario. If the attacker wants to avoid discontinuity, they must synchronize the false signal with the satellite one at the physical location where they will attack the receiving antenna.

If the attacker cannot physically install the spoofer on the vehicle that carries the target receiver unit, they must find another way to determine and track the location of the receiver. There are a few different ways to achieve this, all of which are technically complex. With this wrinkle to consider, it makes perfect sense that there are fewer reports of spoofing than there are of GPS jamming incidents.

Jamming: Casting a Wider Net

Jamming is far more widespread than spoofing, partly because it is nearly effortless for almost anyone to perform on purpose, and partly because it can happen by accident. The case of the New Jersey jammer is an excellent example of both coinciding. While the man purposefully purchased a device with the intent to interfere with the GPS tracking his truck, he also managed to interfere with a much more substantial and pivotal GPS receiver in the process.

GPS jamming is also typically less subtle than spoofing. While the goal of spoofing is to hide activity so the target receiver doesn't realize anything is amiss, jamming causes overt interference. In a military setting, the difference is stark. Spoofing a drone to appear in a different location, for example, might cause the coordinating team to wonder, "How did that get there?" An investigation would take a while to reveal the incidence of spoofing.

However, a jammed drone will drop its signal entirely or otherwise appear compromised in a way that indicates jamming has occurred. While spoofing is more likely to be part of a long-term operation, jamming is more frequently a way to sow confusion or chaos before an imminent attack.

How to Protect Against Spoofing

Combating spoofing requires GPS receivers to be able to differentiate spoofed signals from a combination of legitimate and faked ones. After it has flagged a signal as a spoof, the GPS can exclude it from the process of positioning calculation.

The receivers themselves need protection against spoofing. Multiple layers of protection increase the number of intervention points to detect spoofing. It helps to think of spoofing protection like a home security system. An alarm at the entry is helpful, but adding further measures like motion detection and video surveillance helps provide more detail on attacks and can trace the attack back to its source.

A completely unprotected GPS or GNSS receiver is susceptible to attacks of even the simplest caliber, but fortunately, a variety of secured receivers can alert people and organizations to spoofing. They do this by searching for anomalies in the signal, or through the use of signals specifically created to make spoofing more difficult.

The most advanced and cutting-edge spoofing prevention tech uses algorithms to process signals and detect an array of anomalies. As an example, one of the telltale signs of a spoofed signal is that it's typically stronger than a genuine GPS signal.

Data Authentication

Several countries are tackling the issue of spoofing prevention at the root by choosing to address security at the satellite level. One example is the satellite Galileo, which will use Open Service Navigation Message Authentication. It's the first satellite system to embed spoofing prevention into a civilian signal.

Message authentication involves the sender using a secret key to create an authentication signature. The message and signature travel to the receiver simultaneously, and the receiver must use the same or another key to verify alignment between the message and authentication signature. An authenticated message indicates that:

  • The transmitted message and the received one are identical.
  • Someone with access to the key generated the authentication message.

This technique makes it evident when spoofing has occurred, and with further development, will make it impossible to spoof a signal altogether.

Preventing GPS Jamming

As with spoofing, the way to prevent jamming is to be aware of it. Users can overlook the fact that someone is jamming their GPS, which makes it impossible to rectify. It's essential to set up defenses against multiple scenarios, but finding and characterizing the source of interference when it occurs is a crucial tool in future prevention.

The Cyber Electromagnetic Activities approach provides context to jamming threats. This method addresses three layers. First, there is the cognitive layer, where humans are making decisions based on GPS data. There is also a virtual layer, where GPS data informs a network of systems, and a physical one, which concerns the actual hardware used to provide GPS data as well as protect it. Under this approach, GPS anti-jamming efforts require:

  • Understanding of system weak points and ability to identify jamming for switching over to traditional methods of positioning and navigation
  • Protection of GPS data and verification before use
  • A multi-layered hardware approach that can verify GPS information despite the presence of jamming, without losing significant accuracy

Antenna Systems

Antenna systems present a common and effective means of preventing GPS jamming. Controlled reception-pattern antennas are not your typical antenna. They are complicated and have various elements that shield a GPS or GNSS receiver from the sources of jamming. Complex systems of antennae, referred to as anti-jam antenna systems, use multiple types of technology to foil attempts at jamming. While the military initially developed these devices, their presence is growing in several industries that rely on GPS and GNSS to facilitate or improve operations.

Secure GNSS From Duncan-Parnell

Today, it's more vital than ever to work with reliable GPS and GNSS, no matter what industry you're in. Duncan-Parnell offers top-of-the-line surveying GNSS and GPS mapping accessories for all your needs, and has provided exceptional customer service since 1946. Our 15 locations make it a snap to find what you need. To learn more about our hardware, software, GNSS and other products and systems, call us at 800-849-7708. Successful projects start here.

Back to Blog