# Towards the Unmanned Aerial Vehicles (UAVs): A Comprehensive Review
## 7 Security Challenges and Solutions  
The security and privacy concerns are rarely addressed in the design consideration of small UAVs. UAVs often include onboard wireless communication modules that use open, unencrypted, and unauthenticated channels, rendering them exposed to a variety of cyber-attacks [112; 113; 114]. An intruder wishing to disrupt drone communication has several options for carrying out their malicious aim. For example, the attacker may send out many reservation requests, eavesdrop in on control communications, and/or falsify  
Figure 12: Inspection of power lines through UAV. data. Hacking of drones is another major concerns of using UAVs for data collections and wireless delivery. In military operations, UAVs contain sensitive-information and may become victim of malicious attacks and data theft. Hackers can usurp control of UAV for illegal activities including smuggling, invasion of privacy and stealing stored information. Liability for UAV includes an enormous risk to individual privacy. UAVs are installed with cameras or any device that can capture images or videos; it can violate the privacy of communities or people. To overcome this issue in USA, Center of Democracy and Technology (CDT) informed Federal Aviation Administration (FAA) to implement certain rules to ensure privacy. In this regard, Privacy by Design (PbD) was proposed, which offers remedies for security and privacy breaches [115]. PbD rules significantly limit the privacy intrusion. Additionally, continuous UAVs flights can reveal trade secrets of concerned companies and can severely affect their business. Denial-of-service (DoS) and distributed DoS are the most common attacks on UAVs that occur due to the absence of proper DoS/DDoS resistant mechanisms. DoS attacks cause severe availability challenges as the attacker sends several requests to cause UAV network congestion. DoS attacks are performed by depleting the batteries, overloading the processing units and flooding the communication links to cause huge interruptions. In DDoS, UAV systems faces unreachability issues as the attacker can overwhelm it through traffic from multiple sources. Moreover, signal spoofing through hijacking can damage the nature of certain UAVs. GPS Signal spoofing attack can be performed by inserting or passing false data through GPS channels by the miscreat as shown in Figure 13. In hijacking, the attacker can take complete control of UAV by injecting extra commands. Communication links of UAVs also suffer from session hijacking. These attacks can be mitigated through direction-of-arrival sensing, detection of signal distortion and strong authentication. Among different security issues, Ground Control System (GCS) attacks are very dangerous as the attacker can steal all the data from UAV by using computer running dedicated software. A compromised GCS enables adversary to send malicious and erroneous commands. These attacks are usually performed through key loggers, viruses and malwares. Malicious operating commands can be performed to take control of any victim UAV. These attacks compromise the confidentiality of UAVs through different methods such as social, engineering and malware etc. Necessary countermeasures are required to prevent UAV's data from being leaked to unauthorized processes, entities and users. It can be mitigated by using multiple GCS authentications. Possible GCS threats are shown in Figure 14.  
Figure 13: GPS spoofing attack. In some cases, attackers send erroneous warning messages to misguide UAVs. It creates an illusion for UAVs and can degrade UAVs network performance by causing data traffic jams. These attacks can transmit corrupt data to UAVs as they mislead ground control stations. Moreover, the attacker can send false information which might impact the performance of UAVs. It occurs due to the absence of proper authentication mechanisms. In such attacks, the adversaries can masquerade as a legitimate user to send wrong instructions or commands.