Technologies related to mobile device prevention of contactless card attacks are generally described. In some examples, a mobile computing device may monitor for electromagnetic signals at frequencies used for short range communications with contactless cards. Detection of such electromagnetic signals by the mobile computing device may indicate an attack attempt on a proximal contactless card. In response to detection of such electromagnetic signals, the mobile computing device may automatically generate a disruption signal effective to disrupt communications between contactless card readers and any proximal contactless cards, to thereby foil the attack before sensitive contactless card data is stolen.