Dynamic signature reconfiguration is proposed to combat with eavesdroppers to enhance confidentiality over multi-rate optical code-division multiple-access (OCDMA) networks. The code reconfiguration is achieved by exclusively assigning to each network user a set of orthogonal or pseudo-orthogonal codes and randomly selecting one among them to represent each user's signature. A central node station is assumed to monitor network traffic condition and to signal transceiver coder-decoder pair to perform signature codes changing. We illustrate the confidentiality enhancement by dynamically reconfiguring user signatures using prime-lengths M-sequence codes. When the set of signature codes increases and the eavesdropper's codes detection becomes more difficult, thus network confidentiality is significantly increased.