## 4 Security and Privacy of IoNT
### Security and Privacy Challenges of IoNT  
This section provides an overview of the security and privacy challenges that pose vulnerabilities and provide an avenue for malicious users to compromise the security and privacy of IoNT. In general, a vulnerability refers to the openness or susceptibility to attack or harm by malicious users. Malicious users may try to exploit vulnerabilities present in a nanodevice or a nanonetwork; thus, these vulnerabilities need to be handled by implementing necessary security methods. The challenges to the security and privacy of the IoNT are summarized as follows:  
* Resource limitation
* Due to their diminutive size, nanomachines are constituted of minimal resources, including limited processing power and memory, to perform only necessary tasks. This limits the adoption and integration of built-in security procedures with the IoNT, such as encryption, making such devices vulnerable to security and privacy issues [38; 39; 40; 41]. Additionally, energy consumption is a significant concern since communication devices, such as nanotube-based radios, need substantial power to generate their payloads. Thus, when building IoNT solutions, balancing the tradeoff between available resources and inbuilt security procedures must be taken into account;
* Exposure to the Internet Having continual connection to the Internet is an essential aspect of the IoNT for proper function and information sharing. This continuous connection to the Internet leads the IoNT into a vulnerable state as it paves the way for attackers to exploit available software and hardware vulnerabilities through the Internet [4; 36]. Further, nanodevices are often composed of limited computation and memory capabilities, and without built-in security features, which makes them an easy target for cyber-attacks coming from the Internet [36; 37; 38; 39; 40; 41];
* Key management It is generally agreed upon that the distribution of security keys (e.g., public and private encryption keys) is the fundamental activity at the heart of virtually any key management system. Keys can be disseminated either by key pre-distribution before the deployment or before any data transmission takes place. Both of these methods are viable options. When a key has been compromised, it is necessary to have the ability to revoke access to that key. This problem is still one of the most difficult problems with sensor networks and IoNT systems [4; 17; 36; 37; 38; 39; 40; 41]. Hence, it is vital to describe standard methods for creating shared keys and to explain how keys can be revoked when it becomes necessary to do so;* Secure localization In order to successfully carry out their functions, several applications that rely on nano-communication require the localization of nanomachines [4; 17]. Absolute placement with nanoscale resolution is difficult to achieve due to differences in requirements between traditional sensor networks, which use different coordinate systems, and nanodevices; however, relative positioning may be more applicable. This is closely connected to security and ensures that only adjacent nanomachines are able to interact with one another, preventing interference from remote attackers;
* Lack of encryption Owing to the miniaturized size and limited computing resources of IoNT devices, integration of inbuilt security mechanisms is not always possible as the encryption and decryption processes consume a lot of resources. The failure to encrypt sensitive data shared between nanodevices, whether on the nanodevice itself or nanonetworks, leads to many security challenges that become increasingly problematic, i.e., attackers are able to eavesdrop on the sensitive data that is being exchanged [36; 37; 38; 39; 40; 41];
* Malware threats In recent years, there is a growing trend of malware that targets IoNT solutions, especially microscale devices in nanonetworks. Continuous internet connection has made it easy for attackers to compromise IoNT solutions [36; 37; 38; 39; 40; 41].