Not sure where you are seeing the unknown device state on the Hub but, if shown, use the MAC Address's first three octets to identify the issuing organisation here Wireshark — OUI Lookup Tool, for example 00-06-1B returns Notebook Development Lab. Lenovo Japan Ltd. in which case you would look for a Lenovo device.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
I see this sometimes when looking at the connected devices area of the Hub UI. As 用心棒 has posted you can check the Mac address against the devices you have connected to see which it is. You can then change the name in the Hub UI to one you will recognise in future.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media, I'm a VM customer. There are no guarantees that my advice will work. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks