Remove computer network places

[martinschool]

Hello,
there is someone in my network and i don't know who it is

 

[martinschool]

Hello,
there is someone in my network and i don't know who it is I did not give any permission to this computer to come on my network. I have a netgear 614 v9 router with mac address filtering.
The computer nor the mac address are in my allowed list.
What can i do to prevent this computer to come on my network??

 

[Emerald]

do you have wireless security enabled? have you set a password?