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原文摘要

Integrated sensing and communication (ISAC) is a cornerstone of 6G networks, enabling simultaneous data transmission and environmental perception. However, the ubiquitous radiation of sensing waveforms introduces a critical security vulnerability where the physical existence and characteristics of targets are continuously exposed to unauthorized wardens. Meanwhile, existing sensing-secure methods primarily focus on degrading a target warden's parameter-estimation accuracy, yet they fail to prevent wardens from detecting the target's physical presence. In this article, we first analyze sensing security threats in ISAC systems and survey existing sensing-secure methods. To address the critical gap, we propose a novel security paradigm termed endogenous target covertness. By intentionally harnessing environmental scatterers, such as known objects, ambient backscatter devices, and reconfigurable intelligent surfaces (RIS), as ghost targets, the proposed scheme ensures a low probability that the warden detects the true target for the true target at the warden. This deliberately renders the true target's existence indistinguishable to the warden, while the legitimate base station can extract the true target's response using prior knowledge of the scatterers. We demonstrate the effectiveness of the proposed scheme through a case study, proving that absolute target covertness can be achieved without consuming dedicated jamming power. Finally, we outline key open challenges and promising research directions to realize truly secure, ubiquitous sensing in future ISAC ecosystems.