I have my airport extreme and I was wonder how likely is someone else been leaching off my network? I'm looking at DHCP Clients (not to sure what that means...) but I noticed that the MAC address of my sibling's MacBook client ID is repeated twice with one having no name and another with a name like this "FIRSTLASTAD3D". Is it being spoofed? It has two different IP addresses. Secondly, that computer was not at the house either but at another adjacent house. I use WPA2 security with a strong password and MAC filtering with a small list of allowed devices. Is my wireless network secure or am I vulnerable? Thank you!