A protective plug assembly for use with a Universal Serial Bus (USB) connector. The plug assembly is installed over a terminated USB connector and provides additional shielding for the USB connector, thereby allowing the USB connector to be used in military, aerospace, industrial or other applications in which signal degradation is a concern. The plug assembly is easily installed in the field, as the plug adapter assembly may be preassembled during manufacture. The plug assembly also provides sealing for the USB connector which allows the USB connector to be used in environmental conditions which are not conducive to the longevity of an unprotected connector.