A method for the remote detection, localization and monitoring of critical faults in underground or underwater pipelines, comprising: a. arranging, on the outer surface of the pipeline, a first plurality of passive acoustic sensors capable of detecting the emission of acoustic waves within the range of ultrasounds; b. detecting, by means of said passive acoustic sensors, the acoustic waves (ultrasounds) distributed along the walls of the pipeline with the formation of a critical fault or at the moment of a development of a fault already under control; c. transforming the signals received into electric signals; d. transmitting the electric signals coming at least from the two passive sensors closest to the critical fault, positioned near said fault, to a data collection centre; e. transforming each electric signal received into a digital signal sent to a remote processor system, equipped with software, which identifies the reception time of the signal emitted from the fault, relating to said at least two passive sensors close to the fault, by a measurement of the acoustic intensity of the emission hit; f. identifying and/or monitoring, by means of software, the relative position of the fault that has arisen or that is developing, with respect to said at least two passive sensors which have revealed the sound emission and its distance L (k) from said at least two passive sensors, starting from that furthest away from the fault, by the development of the equation: L k = V k s τ × t wherein V k (s,τ) is the propagation rate of the acoustic waves relating to the sensor k of said at least two passive sensors, depending on the space (s) that the sound waves must cross through the physical means of the pipeline, the propagation time (t) and the time (τ) depending on the service state of the sensor k, g. controlling the service state of the passive sensors by means of one or more active acoustic sensors positioned on the outer surface of the pipeline, which are capable of emitting, on command, acoustic waves (ultrasounds) comparable with those emitted by a real fault. a. arranging, on the outer surface of the pipeline, a first plurality of passive acoustic sensors capable of detecting the emission of acoustic waves within the range of ultrasounds; b. detecting, by means of said passive acoustic sensors, the acoustic waves (ultrasounds) distributed along the walls of the pipeline with the formation of a critical fault or at the moment of a development of a fault already under control; c. transforming the signals received into electric signals; d. transmitting the electric signals coming at least from the two passive sensors closest to the critical fault, positioned near said fault, to a data collection centre; e. transforming each electric signal received into a digital signal sent to a remote processor system, equipped with software, which identifies the reception time of the signal emitted from the fault, relating to said at least two passive sensors close to the fault, by a measurement of the acoustic intensity of the emission hit; f. identifying and/or monitoring, by means of software, the relative position of the fault that has arisen or that is developing, with respect to said at least two passive sensors which have revealed the sound emission and its distance L (k) from said at least two passive sensors, starting from that furthest away from the fault, by the development of the equation: L k = V k s τ × t wherein V k (s,τ) is the propagation rate of the acoustic waves relating to the sensor k of said at least two passive sensors, depending on the space (s) that the sound waves must cross through the physical means of the pipeline, the propagation time (t) and the time (τ) depending on the service state of the sensor k, g. controlling the service state of the passive sensors by means of one or more active acoustic sensors positioned on the outer surface of the pipeline, which are capable of emitting, on command, acoustic waves (ultrasounds) comparable with those emitted by a real fault.