The objective in this paper is to study and develop conditions for a network of multi-agent cyber-physical systems (MAS) where a malicious adversary can utilize vulnerabilities in order to ensure and maintain cyber attacks undetectable. We classify these cyber attacks as undetectable in the sense that their impact cannot be observed in the generated residuals. It is shown if an agent that is the root of a rooted spanning tree in the MAS graph is under a cyber attack, the attack is undetectable by the entire network. Next we investigate if a non-root agent is compromised, then under certain conditions cyber attacks can become detectable. Moreover, a novel cyber attack that is designated as quasi-covert cyber attack is introduced that can be used to eliminate detectable impacts of cyber attacks to the entire network and maintain these attacks as undetected. Finally, an event-triggered based detector is proposed that can be used to detect the quasi-covert cyber attacks. Numerical simulations are provided to illustrate the effectiveness and capabilities of our proposed methodologies.

中文翻译：

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多代理网络物理系统中通信链路上无法检测的网络攻击

本文的目的是研究和开发多代理网络物理系统 (MAS) 网络的条件，在该网络中，恶意对手可以利用漏洞来确保和保持网络攻击不可检测。我们将这些网络攻击归类为不可检测，因为它们的影响无法在生成的残差中观察到。它表明，如果作为 MAS 图中有根生成树的根的代理受到网络攻击，则整个网络都无法检测到该攻击。接下来，我们调查非根代理是否受到威胁，然后在某些条件下网络攻击可以被检测到。而且，引入了一种被称为准隐蔽网络攻击的新型网络攻击，可用于消除网络攻击对整个网络的可检测影响，并保持这些攻击未被发现。最后，提出了一种基于事件触发的检测器，可用于检测准隐蔽的网络攻击。提供了数值模拟来说明我们提出的方法的有效性和能力。