# Resilient Consensus Control for Multi-Agent Systems: A Comparative Survey
###### Abstract  
Due to the openness of communication network and the complexity of system structures, multi-agent systems are vulnerable to malicious network attacks, which can cause intense instability to these systems. This article provides a survey of state-of-the-art results of network attacks on multi-agent systems. Recent advances on three types of attacks, i.e., those on DoS attacks, spoofing attacks and Byzantine attacks, the three main network attacks, are reviewed. Their attack mechanisms are introduced, and the attack model and the resilient consensus control structure are discussed, respectively, in detail, in terms of the theoretical innovation, the critical limitations and the change of the application. Moreover, some of the existing results along this line are given in a tutorial-like fashion. In the end, some challenges and open issues are indicated to guide future development directions of the resilient consensus of multi-agent system under network attacks. multi-agent systems; resilient consensus; secure coordination; DoS attack; spoofing attack; Byzantine attack +
Footnote †: journal: Sensors  
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of all nodes in the network. While high-intensity information exchange is required, it cannot verify the information flow in the system, making the system at risk of security problems. Therefore, it is necessary to study the resilient control structure of a MAS under fault and attack. As for MASs, the cyber attacks that scholars have studied at present mainly include: denial of service (DoS) attacks [11], spoofing attacks [12], Byzantine attacks [13], replay attacks [14], covert attacks [15], actuator attacks [16], communication attacks [16], intelligent attacks [17], policy attacks [13] and so on. Among them, DoS and spoofing attacks are the two most typical and common network attacks in the field of MASs at present. In addition, the Byzantine attack has become an emerging and significant research topic in recent years. Thus, there are tremendous results concentrating on DoS attacks, spoofing attacks and Byzantine attacks. For this reason, this survey focuses on these three kinds of cyber attacks to illustrate the recent advances in these fields. The motivations for the survey are twofold. Firstly, diverse control methods have been developed in the published literature throughout the last decade to explore the defense mechanisms for MASs under network attacks, which are not covered in the existing surveys [18; 19; 20; 21; 22]. Secondly, the related fields are mature enough to deserve a survey classifying the existing analytical approaches, the models used and the results achieved for the MASs under attacks from both systems and control perspectives. The contributions of this survey can be summarized as follows:  
* It develops a comprehensive classification of resilient consensus strategies. The attack types discussed are more basic and comprehensive and can cover many special attacks developed from these three main attacks. * It reviews an extensive set of more than 100 consensus algorithms and discerns the classes they are associated with. The attack mechanism and the corresponding security control protocol are described in terms of the formula definition and algorithm construct. The shortcomings of the control protocols are explained according to the specific parameters, so as to clearly analyze the corresponding security control framework. * The algorithms in the same class are compared regarding their attack types, centralization, scalability and so on. This survey summarizes the main elastic control schemes corresponding to each attack as much as possible, which can be applied to a variety of actual scenarios and attack situations and provide solutions to security control problems. The remainder of this paper is as follows. Section 2 presents the preliminary on graph theory and the consensus problem of MASs. Section 3 is dedicated to reviewing the work on DoS attacks, spoofing attacks and Byzantine attacks.