## 3 Security Attacks on AV Sensors: A Closer Examination of GPS Systems
### Exposure of Light Detection and Ranging (LiDAR) Systems to Security Attacks  
LiDAR systems which are essential components in autonomous vehicles, function as range-finding sensors. By emitting light pulses and measuring the time taken for these pulses to reflect off distant surfaces, they generate a three-dimensional map of the vehicle's environment. These laser pulses, which are produced hundreds of times per second, are typically reflected off a rotating mirror, creating a scan. Extra pulses, referred to as echoes, contribute to the vehicle's ability to detect objects under varied weather conditions [30]. Despite their critical role in facilitating safe autonomous navigation, LiDAR systems are susceptible to potential security threats. One such threat is relay signal attacks, a variation of replay attacks, which aim to misplace targets from their actual positions by rebroadcasting the original signal provided by the target vehicle's LiDAR from an altered location. This attack can be executed inexpensively using just two transceivers, as demonstrated in [31]. Another concerning threat is spoofing signal attacks, an extension of relay signal attacks. An adversary can create phantom objects by transmitting a signal of the same frequency as the scanner. LiDAR systems typically listen for incoming reflections for a minimum of 1.33 microseconds. To successfully inject signals into LiDAR, the false signal must enter this window, which allows an attacker to manipulate the perceived location of objects by delaying the initial signal before relaying it. Such attacks can cause autonomous vehicles to slow down or even stop, potentially resulting in fatal accidents, particularly on highways [32, 33, 34]. Several potential countermeasures can be employed, including the use of non-predictable LiDAR, which skips a pulse but continues to listen for incoming pulses. Another strategy is to reduce the LiDAR pulse time, thereby reducing the attack window in the sensor, although this also shortens the sensor's operational range [31]. Given that LiDAR pulses are not currently encoded, one promising direction for future research is the exploration of LiDAR pulse encoding as a potential means of mitigating these attacks. Figure 3 is a visual representation of the Relaying and Spoofing signal attacks on LiDAR. LiDAR systems in autonomous vehicles can be vulnerable to security attacks, which can have serious implications for road safety. Here are some examples of how security assaults on LiDAR sensors can manifest in real-world autonomous vehicles:  
**Spoofing attacks:** Adversaries can create false signals that mimic the real signals received by LiDAR sensors, causing the autonomous vehicle to misinterpret its surroundings. For example, an attacker could create a fake obstacle close to the front of a victim AV to cause it to swerve or brake suddenly [32]. **Cyber-level attacks:** Attackers can disrupt sensor data by compromising the LiDAR system, even if they lack situational awareness. This can result in compromised perception and tracking in multisensor AVs, which can be critical for road safety [35]. **Electromagnetic interference (EMI):** LiDAR sensors can be vulnerable to IEMI, which affects the time-of-flight circuits that make up modern LiDAR systems. This can force  
Figure 3: Relaying and spoofing signal attacks on LiDAR. the AV perception system to misdetect or misclassify objects and perceive non-existent obstacles, which can be dangerous for road safety [36]. **Adversarial objects:** Attackers can generate adversarial objects that can evade LiDAR-based detection systems under various conditions. For example, an attacker could create an object that appears normal to a human observer but is misclassified by the LiDAR system, causing the AV to make incorrect decisions [37]. To mitigate these vulnerabilities, researchers have proposed various countermeasures, such as probabilistic data asymmetry monitors and security-aware fusion approaches [35].