PC Guardian of San Rafael, California, has introduced a USB-port security system that prevents unauthorized data transfer by physically locking USB ports, thus reducing the risk of data leakage, data theft, computer viruses, and malware. The USB Port Security System protects single or multiple ports while allowing continued secured use of authorized USB devices. The system consists of a port lock, key, spacers, port blocks, and cable guards. Keys can be alike or different for multiple locks, and port blocks and cable guards are available in square and rectangular configurations. Because the system physically blocks the port, there is no need for software installation or updating.