A countermeasure system for jamming an attack unit is provided. The attack unit receives an infrared carrier signal for detection of a target under attack and is vulnerable to countermeasures from another infrared carrier signal modulated by a predetermined modulating signal. The countermeasure system includes a radio frequency source for generating a radio frequency carrier signal, a modulator for modulating the radio frequency carrier signal using the predetermined modulating signal, and a antenna for transmitting the modulated radio frequency signal towards the attack unit.