I use an iPad at home and an app named fing to keep track on the number of devices?

… Hooked to my wifi. I've discovered a device named ARRIS I don't seem to be able to identify as part of the family's devices…

Do you know what it may be? (Is another modem of brand ARRIS juicing my network?)

How should I kick it out and prevent it from re-joining my network?

Should I call a pro?

Thanks in advance! :-/

Read more: I use an iPad at home and an app named fing to keep track on the number of devices?