# Detecting and Mitigating Attacks on GPS Devices
## 4 Factors Contributing to GPS-Denied or GPS-Disrupted Environments
### GPS jamming and Unintentional Interference
One event was particularly interesting because it occurred simultaneously across both locations, which also strongly correlated to an interference signal recorded at test sites throughout Europe, including Belgium, France, Germany, Latvia, Finland, and the United Kingdom. This event was a narrowband interference signal located near the center of the L1 carrier and caused widespread GPS signal disruption or outage for several seconds. The estimated affected area was approximately one million square kilometers. Data were analyzed to determine if this event could have been caused by solar activity or some type of space weather event; however, the source of this interference remains unknown. Several papers in the literature discuss the feasibility of implementing low-cost GPS jammer systems. For example, the authors of [48] presented a study examining the detection and jamming of small commercial UAVs through low-cost commercial GPS jammers. The authors of [45] described results from a study that implemented a GPS attack system against a DJI Phantom 3 quadcopter UAS utilizing low-cost, commercially available hardware and software. The authors used a BladeRF X40 software-defined radio (SDR) platform with signal generation performed within the GNU Radio SDR development environment. The authors of [49] utilized a similar jammer design as reported in [50], using a BladeRF x40 SDR platform and the GNU radio software environment. They implemented various jamming techniques, including barrage jamming, CW tone jamming, sweeping noise jamming, sweeping narrowband pulse jamming, and a protocol-aware jamming waveform that matched the characteristics of the GPS signal structure. The authors of [51] demonstrated an SDR-based GPS jammer developed within GNU Radio. The authors of [52] also demonstrated an SDR-based GPS jammer developed using a BladeRF X40 SDR and GNU Radio. The results of [48] through [49] revealed that effective GPS jammers can be constructed using low-cost commercial (typically black market) GPS jammers or low-cost \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Location**} & \multirow{2}{*}{**AWGN Wideband**} & \multicolumn{2}{c}{**Narrowband**} & \multirow{2}{*}{**Chirp**} & \multirow{2}{*}{**CDMA**} & \multirow{2}{*}{**Other**} \\  & & & & & \\ \hline Site 1 & 16.2 & 9.3 & 0.5 & 0.1 & 0.7 \\ \hline Site 4 & 37.3 & 4.8 & 1.2 & 0.8 & 0.5 \\ \hline Site 5 & 12.0 & 11.9 & 13.5 & 1.5 & 7.1 \\ \hline Site 7 & 12.9 & 43.1 & 2.8 & 1.1 & 1.8 \\ \hline Site 8 & 124.2 & 131.2 & 73.8 & 8.3 & 28.2 \\ \hline Site 9 & 10.0 & 3.7 & 3.5 & 0.5 & 11.0 \\ \hline Site 10 & 42.9 & 23.3 & 38.0 & 3.7 & 23.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean weekly number of different types of interference events from the measurement campaign presented in [44]. SDR hardware and software components. Effective GPS jamming systems are not difficult to implement using low-cost and no-cost open-source components. Table 6 summarizes the various GPS jammer implementations found in the literature. A small number of papers quantitatively study the impact of jamming on GPS receiver performance. Most notable are the research efforts presented by the authors of [53; 54]. The authors of [53] analyzed several different types of jamming against a simulated GPS waveform. They considered four different types of jamming strategies: (1) pulse jamming, (2) continuous wave (CW) jamming, (3) barrage noise jamming, and (4) swept partial-band noise (PBN) jamming. This study demonstrated that CW jamming results in the largest degradation of the GPS signal, closely followed by barrage noise jamming. BER performance asymptotically approached the BER rates as jammer power increased, likely due to the spread spectrum nature of the GPS signal. Further degradation was likely due to the saturation of the GPS receiver's RF front-end hardware. The authors did not consider chirp jamming, which is known to be highly effective against GPS. Table 7 summarizes the effectiveness of the different jammer strategies presented in this study [53].