Disclosed is a method for detecting at least one compromised computer device in an information system, the method including: performing a frequency scan involving dividing the electromagnetic spectrum into frequency sub-bands; performing, in each frequency sub-band, a time envelope demodulation in order to recover signals transmitted by at least one computer device of the information system; converting each demodulated signal in the frequency domain; constructing a frequency spectrum on the basis of the demodulated signals in all the frequency sub-bands; finding, in each frequency sub-band of the frequency spectrum, at least one amplitude line having energy that is greater than a first predefined energy threshold; and, if at least one line having energy that is greater than the first predefined energy threshold is found, indicating the presence of at least one compromised computer device transmitting compromising spurious signals.