# Advanced Persistent Threats and Their Defense Methods in Industrial Internet of Things: A Survey
## 6 Open Research Problem  
IIoT security issues cover a range of IIoT systems, from the physical security of connected nodes or equipment; network communication security; and data security during transmission, transformation, and storage processes, to application security. Due to the highly specialized nature of APTs, it is questionable whether traditional mechanisms are still sufficient to protect recent IIoTs, and this section will discuss open research issues in APTs faced by IIoTs. * The focus of the work is to ensure specific IIoT architecture, including a network-physical-social-based security model [124], focusing on the U2 IoT architecture [125] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Survey** & **Article (Yead)** & **Objective** & **Prospect** \\ \hline A survey on the classification of cyber-attacks on IoT and IIoT devices & [119] (2020) & Aims to recognize the different Cyber-attacks, which are related to IIoT equipment and fully executing IIoT mechanisms & Must understand the different Cyber-attacks that an IIoT network faces to develop new protection mechanisms \\ \hline Intrusion detection and prevention in industrial IoT: a technological survey & [120] (2021) & IIoT systems from different vulnerabilities, threats, and attacks & Expanding the use of artificial intelligence, 5G and blockchain technologies for IIoT security \\ \hline A new proposal on the advanced persistent threat: A survey & [121] (2020) & Proposing a new APT detection model using machine learning techniques & A framework based on the proposed five-stage model is proposed. Also, build data sets to train the ML algorithms used in the framework \\ \hline A survey of advanced persistent threats: attack and defense & [122] (2021) & Introduction to the various stages of attack techniques and classification of detection and defense techniques & Research for more APT attack models \\ \hline A comprehensive survey on attacks, security issues, and blockchain solutions for IoT and IIoT & [123] (2020) & Design the classification of IoT security research fields and the corresponding solutions & Develop robust security solutions to address emerging threats with the latest technology \\ \hline Our work & - & Overview and modeling analysis of APT attacks and defenses for each layer of the IoT system & Combining APT detection technology, blockchain, SG, AI, and big data to defend against ever-evolving APIs \\ \hline \hline \end{tabular}
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Table 7: Advantages, disadvantages, and applications of models. and secure method grid designed to protect SDN-based IIoT architectures [126]. As a single security architecture and framework cannot fix the entire IIoT system, a bottom-up approach is needed to design IIoT security architectures with higher levels of abstraction. The emphasis of the proposal should be on interoperability issues to integrate different security mechanisms supported by IIoT technology and cross-layer security solutions. * The limitations of traditional point-to-point defense systems and security mechanisms. The connections and communications between IIoT networks have recently been protected using traditional network security protocols such as TLS/SSL, IPSec, RADIUS, and IKE. Most of these security protocols are based on point-to-point defense. For example, TLS/SSL provides transport layer protection, and IPSec focuses on the MAC, data link, transport, and network layer of IPv6 and IPv4. As IIoT communication technologies become more diverse, these traditional security mechanisms, which focus on point-to-point defense, are less effective against APT attacks. APT attacks can target any vulnerabilities or weak links in IIoT and application systems, and equipment that has been hijacked or installed with backdoors can easily infiltrate the IIoT. * Lightweight and stronger encryption algorithms. Most IIoT communication protocols and technologies still rely on traditional encryption algorithms such as RSA, MD5, RC4, and DES-56 to ensure data confidentiality and communication security.