Quantum Key Distribution (QKD) protocols are critical for ensuring secure communication against the threats posed by post-quantum technologies. Among these, the BB84 protocol remains the most widely studied and implemented QKD scheme, providing a foundation for secure communication based on the principles of quantum mechanics. This paper investigates the BB84 protocol under a partial intercept-resend attack in a realistic scenario that accounts for system noise. In this context, existing attack detection methods rely on estimating the quantum bit error rate (QBER) in the portion of key bits exchanged over the classical channel to identify the attack. The proposed approach introduces a novel scheme in which the two communicating parties agree on the maximum fraction of shared key bits that can be correctly intercepted by the attacker. This parameter can be configured according to the security requirements of the application. The paper first presents the theoretical model for computing this parameter, which is subsequently used to develop a threshold-based detection method. Unlike other detection methods for intercept-resend attacks, the proposed scheme is independent of the interception density and relies solely on the system noise and the application’s security requirements. Finally, an enhanced version of the Python Quantum Solver library is implemented to test the proposed method using the Qiskit framework. Simulation results demonstrate the high accuracy and very low false negative rate of the proposed method, with a slight degradation in performance observed when the actual interception rate approaches the threshold defined by the security requirements.

link: https://doi.org/10.1016/j.comnet.2026.112058