I operate an internet estore from a rural location. My ISP is a satellite company which means I have a limited data allowance. For the past two months someone has been hacking my network and using up my data allowance. I think they are in Eastern Europe based on some bounced emails. The network consists of a wired Ethernet with a switch connecting two floors and a router to access the satellite modem. There are several devices at the nodes - workstations, NAS, printer - that sort of stuff. Here is what I know.
1. The problem is not entry through WiFi because the allowance continues to disappear when the WiFi radio is disabled.
2. If the problem is in the form of malware then it is malware that isn't found by Norton Security or Norton Power Eraser. All nodes are clear of malware according to Norton
3. I use the Norton firewall. Nothing there seems amiss.
4. If I connect the modem directly to my Linux workstation, the problem subsides until I connect it back to the network.
I'm looking for suggestions on where I might look to find the leak. Thanks for any help.