## 3 System Description
Data tampering: in this case, information collected from the UAV flight can be tampered with in two locations: (a) either in the base station or (b) in the MDAS. It could lead to misinterpretations regarding network coverage or receiving/sending signals in mobile networks. 4. UAV hijacking: this cyberattack involves taking the UAV away from the location used for experimentation to somewhere where a spurious third party can take advantage of it. It will usually involve tampering with the Wi-Fi communications sent and received from the base station or with the GNSS signal; the latter is far less likely due to the extra security that it will make use of. Consequently, security countermeasures must be undertaken to secure the data interchange and collection that takes place within the components of the developed system. Rather than writing any code that would involve the usage of cryptography, security is provided due to the use of several components in the proposed system, which already have built-in security features that will provide securitization to the whole system. Those elements are:  
1. ArduPilot as the base station software: as described in the following section, ArduPilot has been used as the software for managing flights and UAV missions. Specifically, it makes use of a separate Mission Planner module used to conceive flights for specific missions that involve specific movements. As it was said in [24]: _\"ArduPilot and Mission Planner have the ability to add security to over-the-air MAVLink transmissions by adding packet signing using an encrypted key\"_, so this program can enable additional security features. The fact that ArduPilot is an open-source software development also aids in auditing command and information transfers ([25]) in case it is required. Thus, using ArduPilot and its Mission Planner will play a significant role in discouraging tampering with the UAV missions or the data collected. 2. Galileo as the GNSS: not only does it offer a higher degree of signal accuracy for device positioning (in our case, the UAV), but it also has additional security enabled by means of the Galileo Open Service Navigation Message Authentication (NMA), which provides _\"an authentication mechanism that allows a GNSS receiver to verify the authenticity of the GNSS information and of the entity transmitting it, to ensure that it comes from a trusted source\"_ [26]. In this way, security in the communications between the GNSS and the UAV is upgraded and alterations in UAV missions or data collection become more difficult. 3. Wi-Fi as the wireless protocol used to establish communications between the UAV and the base station: the Wi-Fi protocol utilized for wireless communications is the 802.11 ac iteration, which has security enabled in the signal sent throughout the used SGHz frequency band. In this way, communications can be secured in the system at the physical level and will make it more difficult to tamper with the UAV's behaviour or the received data. Credentials for base station access: security capabilities can be added by providing an authentication mechanism that will filter the access to the hardware used, such as the base station. In this way, a first layer of security can be provided that will make it harder for spurious parties to access it, so that base station monitoring and data tampering can be prevented. The security threats that might be faced by the developed system and the countermeasures taken to solve them have been summarized in Table 3.  
Overall, the three subsystems that make up the tool displayed in this paper are described in the following sections.