I have the GlassWire paid software. I am using it to monitor my Broadband with BT (UK provider). There is a cap of 40 GB per month on my useage. Until January this year my broadband useage per month averaged 20 GB. Since January 2016 my useage has soared for no apparent reason, BT cannot explain it either. I am monitoring my useage with Glasswire and also my Ipad and iphone useage [with other monitoring software] when on the network. The total of broadband useage for some days [as counted by my various monitors including GlassWire] is far less than BT say that I have used. I also use BT TV and although that uses broadband, the useage for downloading movies does not count against my 40 GB cap. Yet, the apparent excess broadband useage often coincides with days that I have downloaded movies to watch. BT have said that they will monitor my BT TV use - but don’t seem to believe that they are at fault. I really don’t know what to do next
Since installing GlassWire on your PC did you reboot? GlassWire can’t pick up all network activity in some cases without a reboot. We warn about this on install but don’t force the reboot.
If it were me I’d probably suffer for 2 days and not use any WiFi at all by turning off all my devices, and then check with BT to see what their stats say. If the stats show bandwidth usage then, then I’d explain all my devices were disabled.
Another thing you could do is to change your WiFi password just in case someone else has access.