Intrusion detection

  • Mod

    I've been thinking for some time about the vulnerability of wireless security devices and following this video I have to agree that wired security system is definitely the best way to go. Still it would be nice to monitor in some way if a jammer is creating background noise for a prolonged time and if that is the case then send an alert. Would the receive rssi measurement be enough to detect any unusual strong source of RF noise?

  • I guess you could add a 'heartbeat' signal to the nodes and if more than a certain acceptable number fail to connect you get an alert?

  • Mod

    Sure that is a way that can be used alongside with other systems. I am planning on having the security sensor on cable anyway and heartbeat would be battery consuming as it would need to be sent quite often to have a reliable check. The radio noise monitoring would be an early warning

  • Hardware Contributor

    @gohan said in Intrusion detection:

    heartbeat would be battery consuming
    I would use a bluetooth beacon for that, it uses the same frequency so will be jammed at the same time, and it pretty efficient to send data at short intervals without eating the battery too fast.

  • Mod

    First I don't know how I would do that, second I am using most 433mhz and it is also a widely used frequency on a lot of wireless devices

  • @gohan

    Here is another idea for you to think about.

    Get an RTL-SDR dongle ($10) and attach to an old raspberry pi (or new one!)....

    Set it to monitor the frequency you will use and then either send a message to yourself (sms, email etc) - Or have another tx module on it to send directly to your gateway. This would ofc need to be mains powered, but might work.

    Actually, come to think of it, a simple home made absorption wave meter connected to your system would also be enough to do what you want. Google will give you the details for that....

    I don't know how much traffic you have on the sensors, but a watchdog timer that trips if no data received for x seconds is another approach.....

  • Hero Member

    If you want to detect jamming, just dedicate a module to continuously monitor RSSI.

  • Mod

    That was in my first post: if the gateway keeps monitoring the rssi would that be enough?

  • Hero Member

    I would think so. If you've got a clear channel, there's no jamming. Though I suppose a sophisticated adversary could detect the start of your transmission and then jam just enough to make the CRC go bad. That would be much harder to detect just looking at RSSI. So, really, just sending packets and seeing if they arrive is the surest way to know if something is afoul.

  • Frequency hopping is a form of anti-jam. The nrf24l01+ are capable of this but I don't think it is implemented in the mysensors version.

  • Mod

    Well yes, but nrf24 frequency range is not very wide, it shouldn't be a problem to disturb that. Anyway I was just trying to find a way to detect weird signals. I know good security systems do frequency hopping on a wide range but I guess they don't use any rfm69 or nrf24

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