Multi-Eavesdropper Detection Through PHY-Aware Cell-Free AP Selection

The ability to provide reliable data rates across several coverage areas establishes massive multiple-input multiple-output (m-MIMO) cell-free (CF) systems as a pivotal technology for future sixth-generation (6G) systems. CF networks do, however, introduce additional security and network integrity vulnerabilities. For that, to complement the traditional cryptographic algorithms, physical layer security (PLS) can be an effective strategy for acquiring essential wireless network information in order to develop authentication methods against impersonation attacks. To prevent these spoofing attacks, we propose leveraging the wireless channel and the access point selection (APS) allocation schemes as authentication mechanisms. Our approach begins with a threshold-based analysis of spectral efficiency (SE) losses across different APS schemes. We then propose an algorithm capable of estimating the number of eavesdroppers executing active attacks while identifying the targeted user equipment (UE). Finally, we test the robustness of our detection scheme by examining how SE loss and achievable secrecy SE change when a single attacker is positioned at various locations relative to the targeted UE. Results demonstrate that monitoring these parameters provides critical insights into network performance and the impact of active eavesdropping. These findings highlight the potential of integrating PLS with upper-layer authentication protocols to significantly enhance wireless network security.