# Detecting and Mitigating Attacks on GPS Devices
## 4 Factors Contributing to GPS-Denied or GPS-Disrupted Environments
### GPS jamming and Unintentional Interference  
GPS signals are extremely weak on Earth's surface, often on the order of \(-130\) dBm or lower. A relatively low power emitter can interfere, intentionally or unintentionally, with proper GPS signal reception, exacerbated by the fact that commercial GPS receivers use varying-quality hardware components and signal processing methods, which can lead to poor performance for some receivers in non-pristine electromagnetic environments. Unintentional interference can be caused by malfunctioning or misconfigured equipment that emits energy into the GPS frequency bands. Unintentional interference can be caused by unsuppressed harmonic emissions into the GPS band or intermittent spurious out-of-band emissions from RF equipment. Unintentional interference can be difficult to detect or locate due to the highly temporal nature of the interference, especially if it is caused by mobile equipment or human activity. Intentional GPS interference, also known as GPS jamming, is typically one of four types: (1) barrage jamming, (2) continuous wave (CW) or tone jamming, (3) chirp jamming, and (4) protocol-aware jamming. Barrage jamming involves the transmission of noise across a wide bandwidth, covering the entire target signal's channel bandwidth. CW jamming focuses the interference energy into a very narrow bandwidth within the target signal's channel. Chirp jamming is an approach where the interference frequency changes rapidly over time. Chirp jammers are often narrowband; therefore, they resemble a swept-tone signal. Protocol-aware jammers attempt to utilize the target signal's attributes to optimize their jammer waveform. There is wide agreement that GPS is susceptible to interference; however, only limited studies on the topic of GPS interference exist. The authors of [44] presented the results of a measurement campaign conducted across Europe over two months in 2016. The authors established eleven signal detection sites across seven European countries: the United Kingdom, Sweden, France, the Czech Republic, Poland, Slovakia, and Finland. Site locations included airports, near major roads, above motorways, busy city areas, and urban areas. Continuous spectrum monitoring and capture were conducted, and the resulting data were processed to determine interference events and attempt to classify the interference type. Over 5000 interference events were recorded over this period, with over 1000 classified as significant interference events, with positioning errors of hundreds of meters or complete GPS disruption near the receivers. The authors of [44] analyzed and identified the different types of interference events. Table 5[44] summarizes the mean weekly occurrence rate for different types of measured interference events. These various interference events had different durations and power levels. Many of these events were ultimately deemed unintentional interference, such as the wideband noise and narrowband signals in the two leftmost columns of Table 5. The detected chirp signals are likely from GPS jammers since chip signals are common for GPS jammers sold on the Internet (black market) [45; 46]. The results of this type of measurement campaign vary across location and time; eleven randomly chosen locations had different results. Two important conclusions can be drawn from the results of this measurement campaign: (1) unintentional GPS interference is a common occurrence, and (2) intentional GPS interference, such as GPS jamming, is not a rare event. A similar measurement campaign was performed by the authors of [47], primarily focusing on two locations in the Czech Republic over 140 days in 2021. During this time, 2158 interference events were reported, 872 of which were deemed high-impact events that caused GPS accuracy degradation or outages.