In this paper, we investigate proactive monitoring to mitigate malicious activities in integrated sensing and communication (ISAC) systems. Our focus is on a scenario where a cell-free massive multiple-input multiple-output (CF-mMIMO) architecture is exploited by malicious actors. Malicious actors use multiple access points (APs) to illegally sense a legitimate target while communicating with users (UEs), one of which is suspected of illegal activities. In our approach, a proactive monitor overhears the suspicious UE and simultaneously sends a jamming signal to degrade the communication links between the APs and suspicious UE. Simultaneously, the monitor sends a precoded jamming signal toward the legitimate target to hinder the malicious sensing attempts. We derive closed-form expressions for the sensing signal-to-interference-noise ratio (SINR), as well as the received SINR at the UEs and overheard SINR at the monitor. The simulation results show that our anti-malicious CF-mMIMO ISAC strategy can significantly reduce the sensing performance while offering excellent monitoring performance.

翻译：本文研究利用主动监控技术来缓解集成感知与通信（ISAC）系统中的恶意活动。我们聚焦于一种场景：恶意攻击者利用无蜂窝大规模多输入多输出（CF-mMIMO）架构，在通过多个接入点（AP）与用户设备（UE）进行通信的同时，非法感知一个合法目标，其中某个UE被怀疑从事非法活动。在我们的方案中，一个主动监控节点窃听可疑UE，并同时发送干扰信号以劣化AP与可疑UE之间的通信链路。与此同时，该监控节点向合法目标发送预编码的干扰信号，以阻碍恶意感知企图。我们推导了感知信号干扰噪声比（SINR）、UE处的接收SINR以及监控节点窃听到的SINR的闭式表达式。仿真结果表明，我们提出的抗恶意CF-mMIMO ISAC策略能够在提供优异监控性能的同时，显著降低恶意节点的感知性能。