The aim of the invention is to create multi-spectral fog walls, in which the threat direction, threat distance, wind direction, wind speed, driving direction, and driving speed are taken into consideration in the dispensing of the visual and infrared line-of-sight interruption over time and space. In order to determine the effectiveness or effectivity of the fog wall (11, 13), a camera (4) and/or a thermal imaging device (5) is combined with a known launcher (2) and the images of both are evaluated in a computer (3), wherein in the evaluation of said information, the fog wall (11, 13) is stabilized or expanded if certain criteria are not reached. The production of a fog cloud (11, 13) that is opaque in the visible wavelength range but that has a residual transmittance is manipulated by cleverly choosing or selecting and adjusting the fog substance (a) itself, the fog concentration (c
1 , c
2 , c
3 ), the thickness of the fog wall (d
1 , d
2 , d
3 ), and the concentration of infrared particles over time and space during the fog burn-off. Disturbances are substantially eliminated by the digital image processing of a thermal image on the friendly side, and the thermal image is thus optimized.