You can't change the name in SecurityCenter. The name reflects whatever name that particular machine has been given by its owner.
Also you can't kick someone off the network. If you know the IP I guess you could block it in the firewall. Or you could simply hide that item.
If you are not actually using the network then simply stop trusting it.
Sorry this took so long to get answered but it would have been noticed earlier had it been posted under whatever version of SecurityCenter you are using.