A protective module for a data transmission port includes a plugging element and an unlocking element. The plugging element includes an extension portion and an end portion. The extension portion is inserted into the data transmission port. The end portion obstructs an opening of the data transmission port and is made of a first magnetically attracting material. The unlocking element includes an attraction portion adapted to attract the end portion and made of a second magnetically attracting material. The end portion of the plugging element escapes from the data transmission port as a result of magnetic attraction between the end portion of the plugging element and the unlocking element as soon as the unlocking element approaches the plugging element plugged into the data transmission port. Therefore, the protective module prevents external devices from getting connected to the data transmission port and prevents dust intrusion.