A new ARRIS device connected to my wifi

There was never an outcome to the post about this in the past.

after a restarting/troubleshooting I had an arris device connect to my network as this has never happened previously.

I paused the device but want to ensure my network is secure from interlopers. My network has passwords for both bands so this is weird.

I have Comcast tv but limited to ten channels and using a small cable box and no WiFi ( I assume).

a pic of the arris device information is below. The last six characters of the Mac address are different to that of my arris xfinity router, so I assume it is not mine.

thank you and please advise.