Why does my Amazon Smart Plug cause FingBox to alarm?

Hi @SidersC
If the smart plugs that are connected are able to connect to internet that means they have an ethernet card (NIC) card in them. So, any device which has ethernet card in them has the ability to direct traffic through them and it might cause the gateway change alerts.

A gateway is a device that routes traffic between two separate networks. The best example of a gateway within your home network is your router. This acts as a gateway between your own personal network and your broadband provider’s network.  

So when you receive an alert from your Fingbox that a new gateway has appeared on your network it means that a device has become a gateway. This could be something usual (e.g. some triband routers have an interchangeable pool of addresses that change a lot), or could be coming from a device which redirects everything to itself (e.g. a hardware firewall), or could be a device that has been attached to your network that you weren’t aware is redirecting all the data.  

Fingbox will alert you when it notices a new gateway so you can investigate if it is coming from a trusted or malicious source.  
 
When a new device joins a network, then it tends to distribute traffic through itself. If you do not know what the new gateway is, check to see if a new device has recently joined your network – this most likely will be the source of the new gateway. If it is a device you do not recognize then block it straight away.