## 7 Security
### Countermeasures  
Intrusion detection systems (IDSs) are developed and used to detect activities and potential cyberattacks. Their main goal is to identify and explore connections associated with types of cyber threats [131]. To achieve this, various approaches are used. One approach is the rule-based IDS, which enables communication, between vehicles (UAVs) and unmanned ground vehicles. It focuses on detecting the insertion of data related to signal strength [132]. For example, the BRUIDS [133] system evaluates how well a UAV can survive an attack. However, this rule-based system has limitations in detecting attacks. It requires human intervention for configuring rules. Another approach is the signature-based IDS, which relies on matching signatures or patterns of known attacks against the content of network messages [134]. If a match is found, it alerts the network administrator. Like the rule-based IDS, it may be less effective against types of attacks that do not resemble existing patterns. For instance, in the Air Force, ADS B technology has been used to detect the transmissions of messages. The third approach is the anomaly-based IDS, which aims to identify behaviors in networks or systems as signs of an attack. This method involves training a model to understand behavior so that it can recognize anomalies when they occur [134]. As a measure against denial-of-service (DoS) and distributed denial-of-service (DDoS) attacks and jamming, this approach is implemented. To ensure the functioning of both unmanned aerial vehicles (UAVs) and unmanned ground vehicles, it is crucial to utilize algorithms that can detect anomalies. These anomalies include several measurements, such as changes in engine temperature. Additionally, these vehicles can benefit from identification systems for traffic analysis [135]. They can also make use of specifications-based systems equipped with embedded sensors and actuators. When it comes to securing data and communication for UAVs and unmanned ground vehicles, the process goes beyond protecting the network. Measures need to be taken to prevent interception and to safeguard sensitive information. An algorithm that addresses transmission challenges over channels like 5G between the vehicle and the ground station based on the block coordinate descent method and sequential convex optimization may be used [136]. This algorithm minimizes functions that are dependent on variables by solving problems in blocks while optimizing a group of variables at each step [137]. Another approach used to maintain data confidentiality during communication is functional encryption [138]. This algorithm optimizes variables such as transmitting power or vehicle trajectory. In areas where UAV-assisted heterogeneous networks (HetNets) require security, this can be enhanced through secured functional encryption techniques that incorporate ECC, digital signatures, hashing, and other encryption mechanisms. These measures enhance security. Also, they protect against malicious activities while encrypting data [139]. When it comes to dealing with both UAVs and unmanned ground vehicles, there are several ways to take countermeasures [140]. One option is using drone catchers or vehicles equipped with nets to capture the vehicles if necessary. Another approach is using drone defenders that emit radio waves disrupting the remote control signals and rendering the vehicle inoperable. Additionally, a fence connected to a cloud-based unmanned aerial system (UAS) can detect any attempts by the vehicle to cross boundaries and disable it [141]. Among the most prominent attempts, there are the following:* Wi-Fi jamming: This is the most common method used, and it operates at a frequency of 2.4 GHz. It is the jamming of wireless transmission signals sent between devices connected to a given Wi-Fi network [142]. It is also used, for example, to protect the network from unauthorized access. The disadvantage is that such interference is visible and can be easily detected.