I would like to setup a simple alarm system using something like a Raspberry Pi or Arduino, some sensors, and a SIM module to send me an alarm when an intrusion is detected.

If I were dealing with an adversary using a Cell-Site Simulator/IMSI Catcher or a signal blocker, would they be able to prevent the system from working? Particularly, can they prevent the alarm/message from reaching me?

What can I do to ensure the system works even in the presence of IMSI Catchers/Cell-Site Simulators/signal blockers?


1 Answer 1


Radio signals are public and prone to a number of issues. Not just the complex simulators you ask about, but a $10 home-made signal blocker can prevent your system from transmitting (or even a 30 yr old microwave).

The way to avoid this is to have a wired backup line or a detection process to detect signal interruptions.

A heartbeat signal to a monitoring process would alert you if the system failed or was blocked from transmitting. You then need to devise a response function for when the heartbeats stop coming in, but that's the general design pattern for this problem.

  • Hi. Thanks for answering. How would a device monitoring signal interruptions to wireless signals, particularly GSM signals, work? Where can I start learning about this?
    – user942937
    Commented May 3, 2019 at 9:58
  • Where are you sending the signals from the system? That's where you send the heartbeat...
    – schroeder
    Commented May 3, 2019 at 10:09
  • How can I know when the signal is being intercepted (in the case of Cell Site-Simulators/IMSI Catchers) or blocked?
    – user942937
    Commented May 3, 2019 at 13:52
  • You can't tell if it is intercepted. You would have to have a process on the system to inspect the tower and confirm its legitimacy or at least that it is different from normal. I'm not sure if the process to do that.
    – schroeder
    Commented May 3, 2019 at 13:53

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