Do you have the guest network turned on within the Virginmedia router? What about the free wifi settings? Perhaps a third party is connecting for free & this is causing the malware notification.
Check the IP address &/or name of each connected device.
Doesn't the guest network functionality use a completely different network (incl. WAN address?)
Agree though, assuming you're using the hub in modem mode and are using the Nighthawk as a router, log into the nighthawk and review all of the clients that are connected - look for anything that you don't recognise - you seem to know what should be connected to the network, validate that only those items are connected and there aren't any "unknown" devices on the network - if there are, investigate what they are - if necessary, block the MAC address of the unknown device so that it's not able to connect to the network.
Another option would be to change your WiFi password and re-connect all of your devices..
Unfortunately, the notification from VM isn't particularly helpful, it doesn't tell you *what* malware is being detected, which might enable you to narrow the search somewhat..
Are you the sole user of the network? Any kids that might be getting up to things that they shouldn't? 🙂
Thanks so much - I do periodically check the devices list on the Nighthawk - In the past there have been grandsons and airbnb guests etc briefly connected, so I thought it might be coming from one of them, but now in lockdown, I'm still getting the letters.
I'll have another root through. Good place to start. Then maybe change the network passwords.
However Virgin only complain about the malware once every 5 or 5 weeks, so it's difficult to know what has worked.