The principle of HF and GSM jamming systems (also known as signal jammer) is to send a stronger signal in the same frequency range in order to drown out the original signal between the transmitter and receiver without drowning out the wire to make the exchanged frames inoperable. An increasingly used method with which certain alarm systems, but also many peripheral devices, can be neutralized with the help of radio waves (GSM transmission, home automation devices, remote controls, WLAN, etc.). So far, it is simply impossible to prevent this type of attack. However, protection scenarios are provided to counter this without preventing Jammer from interfering with wireless alarms. For example, if we try to interfere on the 433 or 868 MHz frequency for X minutes, the sirens will go off and the disturbance notifications will be sent to the user and / or a monitoring station.

If the GSM connectivity part is also encrypted, the wireless alarm sends on a different channel (IP, PSTN, 3G, 4G, Sigfox ...) and allows the user to warn. If unfortunately only one transmission channel is selected and it cannot transmit, the information will only be sent during a return to normal or after the end of an interference attempt. Jamming wireless alarms is the easiest method to implement because of its simplicity, cost, and time ratio. Using a wireless jammer can mask many radio frequencies. Fortunately, as we've seen in this section, alarm device manufacturers can, for the most part, provide a reliable response that allows them to protect themselves from such attacks.

Less known and more insidious or undetectable for certain wireless alarm systems, attacks of the type "SDR" for Software Defined Radio (in English Replay Attack or Playback Attack) aim to hear and intercept the HF radio spectrum using an SDR transmitter / receiver with audio bands from 300 MHz to 928 MHz and support for ASK, OOK, GFSK, 2-FSK, 4-FSK and MSK modulations. In conjunction with a software suite, standard RF signals are decoded and then "played back" and passed back to the alarm system for control. Sources such as "RFCat" can easily feed RF signals back in without the need for complex devices. This type of attack, although less common, will not be recognized as an attempted interference by wireless alarm systems because a legitimate radio signal sent by a remote control cannot be distinguished from that of an illegitimate computer.

Thus, a user who "disarms" their alarm system with their remote control (sending an RF radio signal to the control panel) could be intercepted by that signal and then replayed for malicious purposes. The deactivation by the user (impermissible) is archived by the alarm center and regarded as "normal". "Signal retransmission" attacks are quite common among our neighbors across the Atlantic, but remain marginal (at the moment) in our area. Attacks facilitated by the advent of available devices and affecting many areas, from home automation to certain types of automation, alarm systems, car keys, gate openers, etc. Systems that do not take countermeasures against this type of attack highlight the inherent errors that natively inherit many connected objects, sensors, alarm systems and the like. Fortunately, many manufacturers of security, home automation, or other products offer particularly effective responses to protect against such attacks. Care should be taken when purchasing wireless devices to avoid creating real screens at home. The choice of an "anti-jamming" alarm that also takes this variable into account will prove necessary.